Maybe they think it's legal, OR they know its illegal but possible fines don't put them off and are accounted for as cost of doing business.
Perhaps it's just enough in the grey-zone that it is a "cross that bridge when we come to it" issue and that they don't need to figure out the specifics of any laws/regulation, because if they are on the wrong side of it, in the past it has been proven that these types of regulations are quite toothless.
This specific issue on its face seems a security thing, where users are warned against installing software from untrusted (as defined by microsoft) sources. It very handily doubles as a way to scare users into not installing competitors for their own applications (like browsers and office packages), of course.
Unless part of the calculus involves executives behind bars, I don't know what else we should expect from corporate behaviour; they're just following their incentives.
Uber was (relatively) vocal about their hope for regulation to catch up with this new world of taxi gigs ordered through an app.
And in the MS browser-choice case, the regulation was specifically designed for Microsoft and they had been found to be non-compliant once already.
How does that change the calculus? Clearly, not enough.
You can coordinate this with a coded message, such as:
"Our goal for 2023 is to make Edge a market-leading product, the best browser on Windows, and the customer's browser of choice. All executives ranked Vice President or above will receive $100,000 in shares for every percentage point increase in US browser market share this financial year."
Later you will be shocked - SHOCKED - to learn anti-competitive behaviour happened, when you were "just trying to encourage the OS and browser teams to cooperate on things like power efficiency and security"