There’s an ongoing problem with election integrity conversations. Vote By Mail is a term used to describe a system in which EVERYONE votes by mail, however, absentee ballots is the term used to denote when someone specifically needs to apply for an absentee ballot while opting not to vote at the polls.
The two terms do not mean the same thing anymore. Mainly because Vote-By Mail proponents have hyped the new terminology, probably because some marketer polled to find out which term played better to the voting public.
Anyway, absentee ballots are a type of voting by mail, but Vote-By Mail systems, generally either encourage their use, or mandate it. Therein lies the rub.