It is not. The headline is completely inaccurate.

Nothing has changed for LTS at all. Scroll down to the pretty graphs on https://ubuntu.com/about/release-cycle, and pay particular attention to how the ratio of orange to purple on the LTS graphs has changed over time. (it hasn't) The base LTS support window has always been 5 years, and the extended window has always been another 5 years.

What they did add was additional security updates for Universe packages, which are represented by the black line. Note that this black line is independent of the LTS coverage. From https://discourse.ubuntu.com/t/ubuntu-pro-faq/34042:

Your Ubuntu LTS is still secured in exactly the same way it has always been, with five years of free security updates for the ‘main’ packages in the distribution, and best-effort security coverage for everything else. This has been the promise of Ubuntu since our first LTS in 2006, and remains exactly the same. In fact, thanks to our expanded security team, your LTS is better secured today than ever before, even without Ubuntu Pro.

Ubuntu Pro is an additional stream of security updates and packages that meet compliance requirements such as FIPS or HIPAA, on top of an Ubuntu LTS. Ubuntu Pro was launched in public beta on 5 October, 2022, and moved to general availability on 26 January, 2023. Ubuntu Pro provides an SLA for security fixes for the entire distribution (‘main and universe’ packages) for ten years, with extensions for industrial use cases.

You can also dig into this AskUbuntu answer for even more details, but the long and short of it is this has no impact on Ubuntu LTS whatsoever. Keep using it if that is your thing. Keep using something else if it is not.

Edit: This old news will become newsworthy if Canonical starts shifting packages out of the main repo and into universe, which would in fact reduce the security update coverage of LTS releases. That said, the article has not asserted any evidence of this. Nothing to see here...for now.