The Pennsylvania constitution states:

The Legislature shall, by general law, provide a manner in which, and the time and place at which, qualified electors who may, on the occurrence of any election, be absent from the municipality of their residence, because their duties, occupation or business require them to be elsewhere or who, on the occurrence of any election, are unable to attend at their proper polling places because of illness or physical disability or who will not attend a polling place because of the observance of a religious holiday or who cannot vote because of election day duties, in the case of a county employee, may vote, and for the return and canvass of their votes in the election district in which they respectively reside.

It conspicuously does NOT state that these are the only reasons for which a voter may receive an absentee ballot. The Legislature shall provide a manner in which voters may cast their vote when they are absent from the municipality of their residence or because they are unable to attend their polling places for the above reasons. The Legislature certainly may provide for absentee voting for any other reason, if they so choose.

And if Trump had won the state? There would not now be a lawsuit against any absentee ballots he may have received. That's the central point in all of these actions. The rules were set ahead of time. The time to object was before November 3, not once your team lost the game.