Literally the only reason they can argue Chrome is more secure than Firefox in that kind of setting is because they can Google can push Google Chrome profiles via Google Workspaces but they’ve never working with Mozilla to create an interop for Firefox.
When Microsoft did this with Windows, AD, and Internet Explore, it was deemed a breach of anti-trust laws. The question is whether such laws apply to Google given they don’t have a monopoly in the identity services domain.
If you’d asked me 5 years ago, I’d have said “no way”, but recent judgements with Apple and their App Store lead me to think there is still hope. Regardless of how remote that might be.
And Google would probably say the same thing Microsoft used to say back in the day. Their customers aren't asking for the ability to manage profiles in Firefox. I wouldn't doubt for a second that it's true.
Almost nobody outside of the minority of internet users fighting against chromium hegemony cares about Firefox. Firefox lost its casual users years ago. Hell, even most of those people sticking with it out of principle are doing it while gritting their teeth. It's been a subpar browser for a long time and the Mozilla organization kinda sucks.
Why would any for-profit enterprise waste their time or money on Firefox?