It used to be that to vote by mail, the only way was "absentee voting" where you had to be out of the state on Election day in order to do this. It had the name "absentee ballot" because the voter was away, and the mechanism to vote was by mail. The lines have blurred overtime. In Maryland, for example, the law was changed about a dozen years ago to permit any Marylander to vote by mail, even if he were not going to be "absent". That's the way I've voted for years, because it is so much more convenient for me.
So it seems that Trump's love of absentee voting, in Florida and Republican-run states at least, and hate for mail-in voting, is a distinction without a difference. In other words, his usual BS. The irony of course is that according to much reporting, scaring people off mail-in voting will hurt him and Republicans more than Biden and the Dems.