I've looked it up and it's even uglier and I can kinda understand why they did it this way Basically, for their "integrations" they aren't using any official APIs. Instead they just use the websites and automate them via the Playwright framework. So for each user they have a VM running with a Chrome browser to access the services. So now they have the problem that they need to get their users session cookies into the browser. And the easiest solution for that is having the users access their VM via VNC and just log into the automated browser.
This is such a hacky solution that I'm actually in awe of it's shittiness. That's something you throw together in an all-nighter during a Hackathon, not a production ready solution