https://www.fastmail.help/hc/en-us/articles/4406536368911-Ma...
Even before this, Fastmail supported subdomain aliasing. Which you could have on any email host that has customizable forwarding. Including Google Suite (although with GS sending emails from such "aliases" will fail DKIM, not ideal):
https://www.fastmail.help/hc/en-us/articles/360060591053-Plu...
The effect is that you're not going to reuse the same email address. Granted, this may not help with anonymity when the address is reviewed by a human. But anonymity is getting harder anyway, e.g., Gmail requires activation via a phone call, so you have to trust Google to not share your profile.
Once upon a time, Twitter was not releasing back unused usernames. But now they've announced that they are. Also, Yahoo. Gmail is well behaved, but it's incredibly frustrating to create a new Gmail username. Sooner or later Google will at least think about reusing usernames, and you won't have any control over it.
On domains, I register my personal domain names for 10 years in advance. If I'd die now, my family would have about 9 years to take control, if it helps them in any way; and if not, then why would I care?