Their support also drops certain alias emails, so there's no way to appeal.
A "decentralized" network that locks you out for using basic email privacy tooling, with zero recourse, is centralized where it counts.
You can create an account with any email address you want if you host your own PDS or you can find another PDS that someone else hosts that is willing to register you an account.
One participant's new account spam protection has nothing to do with the network at large being centralised
Side note: it hasn't been called BGS for a very long time. Nowadays they are just called relays and since sync 1.1 the cost for running a relay decreased by multiple orders of magnitude.
In practice, the vast majority of handles (98.9% as of 2024) are under bsky.social [1]. Yes, alternative PDS providers exist, but if the default onboarding funnels everyone into one provider, and the average user doesn't even know what a PDS is, then decentralization is an implementation detail, not a user-facing reality.