Getting to do some real world test in russia before actually needing them in china is probably not a bad idea.

Even if Ukraine only received and used a pair of these missiles, Russia would have to react to the possibility that Ukraine received many many more. This could be a positive development for UA ground forces just like we're seeing TU-92 and TU-22 being operated at more distant airbases and Sevestapol being emptied in favor of Novorossiysk.

I haven't read any expert discussion, but I am wondering if that will be such a problem. That was an issue for ATACMS, but:

• PrSM, which I understand to be the ATACMS replacement, was subsequently accepted by the Army.

  https://www.twz.com/one-argument-against-giving-atacms-to-ukraine-is-about-to-erode

  The pending arrival of the U.S. Army’s new Precision Strike Missile (PrSM) could reduce some of the readiness risks that are associated with a potential transfer to Ukraine of older Army Tactical Missile System (ATACMS) — the tactical ballistic missile that PrSM intends to replace — according to the U.S. Army’s top weapons buyer.

  The Ukrainian government has been actively seeking ATACMS for many months. The weapon has a significantly greater range than most of its existing ground-based strike options and it hits much harder. However, U.S. officials have repeatedly demurred, often citing the small size of its stockpile of these strategically important munitions, among a number of other major factors.

  Douglas Bush, the Assistant Secretary of the Army for Acquisition, Logistics, and Technology, talked about his service’s work on PrSM and the possibility of sending ATACMS to Ukraine to The War Zone and other outlets at a media roundtable earlier today. This comes as Ukrainian President Volodymyr Zelensky is in the United States, first for the U.N. General Assembly’s annual high-level week. He is set to meet directly with U.S. President Joe Biden, as well as members of Congress, later in the week, engagements where the matter of ATACMS is expected to come up again.

  U.S. decision-makers have to weigh “inventory versus potential military plans” when considering whether to transfer those ATACMS to Ukraine, the Bush said today. However, “as PrSM Increment 1 comes on, it might make it less risky from a readiness standpoint to provide some number” of ATACMS to the Ukrainian armed forces.

• It sounds like we've also ramped up ATACMS production since then.

  https://breakingdefense.com/2024/04/sullivan-says-ukraine-supplemental-should-cover-all-of-2024-long-range-atacms-now-in-ukraine/

  “Until recently, as we’ve said, on many occasions, we were unable to provide these ATACMS because of readiness concerns” Sullivan said. “But behind the scenes, the administration across the board has worked relentlessly to address those concerns. We now have a significant number of ATACMS coming off their production line and entering US stocks. And as a result, we can move forward with providing the ATACMS while also sustaining the readiness of the US armed forces.”

In the case of JASSM, it's not ramping up production of a weapon with a large stockpile relative to production rate and limited production that's on the edge of being phased out, but a new weapon (well, in the case of the -ER variant); I'd guess that it's probably less painful to increase the rate of production if we need more for China.

https://www.lockheedmartin.com/en-us/news/features/2024/ramping-up--lockheed-martin-steadily-increasing-production-o.html

Ramping Up: Lockheed Martin Steadily Increasing Production of High-Demand Systems

February 15, 2024

“Lockheed Martin remains committed to ramping production of high-demand systems, like HIMARS, Javelin, GMLRS, PAC-3 and more,” said Lockheed Martin Chief Operating Officer Frank St. John. “In 2024, we are on track to double HIMARS production, have increased Javelin’s production to 2,400 units per year and will deliver more than 10,000 GMLRS.

JASSM and LRASM

As one of Lockheed Martin’s first cruise missiles, JASSM has experienced over 20 years of successful partnership with the U.S. Air Force, providing continued significant long-range, precision engagement capabilities in air-to-ground warfare. As a precise, stealthy and survivable cruise missile, LRASM provides multi-service, multi-platform, and multi-mission capabilities for offensive anti-surface warfare. In support of critical weapons capacity for our nation and allies, JASSM/LRASM is positioned to increase production capacity. To demonstrate our commitment to support munitions supply, we opened a 225,000-square-foot advanced manufacturing facility and prepared our supply chain to maximize our mature production line, increase throughput and ensure quality control.

https://www.twz.com/air/jassm-stealth-cruise-missiles-now-on-the-table-for-ukraine-report

It’s unclear at this point if Washington will decide to provide Ukraine with AGM-158s, but today’s reports are, at the very least, the strongest indication yet that the issue is very much under discussion, and JASSM-armed Ukrainian F-16s are becoming closer to reality.

I mean, the "Arsenal of Democracy" rhetoric reminiscent of World War II is, I think, a bit overheated -- as I've pointed out before, if the US allocated a comparable level of GDP to military production to what it did in World War II, it could support hundreds of concurrent conflicts at the scale it is of the Russo-Ukrainian War. 2024 isn't 1944. But capacity has indeed been coming online; it's not static.

I'm not sure I understand. Did you maybe paste the wrong URL? That's a link to the same article that OP linked to.