Now as far as your hypothetical, sure they can, but I use all of those services, YouTube, Gmail, Maps, ... on Chromium every day and they do not block nor have they ever blocked any of them.
[1]https://twitter.com/addyosmani/status/1133782407419613184
> And it may even be a quick ‘n dirty deliberate hack to exclude Chredge this way, just so it doesn’t pollute their telemetry / testing of new website features.
That test proves nothing without seeing the Google's code. Feature detection is incredibly slow, requiring JS and multiple round trips. Whereas user agent strings are instantaneous.
Read the reply too. ;)
Turning the block on was intentional, and turning it off was intentional.
We can only guess at their motivation, and I can guarantee you it was not benevolent given what Mozilla said recently about their interactions with Google.