I checked into NY and PA, it seems like these two states have introduced a second type of mail voting. From PA website
Mail-in ballot: Any registered voter may apply to vote by mail in the next election. You do not have to provide a reason for why you want to vote by mail ballot.
Absentee ballot: If you will be out of your municipality on Election Day or if you have a disability or illness that prevents you from going to your polling place on Election Day, you can request this ballot type, which requires you to provide a reason for why you want to vote by mail ballot.
This map appears to be covering Absentee ballot restrictions - not all mail in voting options.
I checked into NY and PA, it seems like these two states have introduced a second type of mail voting. From PA website
Mail-in ballot: Any registered voter may apply to vote by mail in the next election. You do not have to provide a reason for why you want to vote by mail ballot.
Absentee ballot: If you will be out of your municipality on Election Day or if you have a disability or illness that prevents you from going to your polling place on Election Day, you can request this ballot type, which requires you to provide a reason for why you want to vote by mail ballot.
This map appears to be covering Absentee ballot restrictions - not all mail in voting options.