Typically this thinking is mostly correct - e.g. Manifest v3 - but not in this case. If websites see enough users using chormium, via user agent or other fingerprinting, they’ll be more willing to require WEI. And unlike Manifest v3 etc. this affects the whole web, not just users of one browser or the other.
In every case monopolies are bad. Including in tech.
Even as an (older) zoomer in the US, this was never a thing for me. No one cared what phone you used. If you had an Android you wouldn’t be in iMessage group chats but no one judged you for it.