I think this might provide more context which you are looking for (and your suspicion seems spot on!):
> This means more writes to do on updates and makes access to old row versions quite a lot slower, but gets rid of the need for asynchronous vacuum and means you don't have table bloat issues. Instead you can have huge rollback segments or run out of space for rollback.
> This means more writes to do on updates and makes access to old row versions quite a lot slower, but gets rid of the need for asynchronous vacuum and means you don't have table bloat issues. Instead you can have huge rollback segments or run out of space for rollback.
https://stackoverflow.com/questions/25153532/why-is-it-a-vac...
Edit: Just wanted to explicitly call out that the Robert Haas article linked in the answer is excellent (I am still reading my way through it).