Many different sites (I use rotowire) give you confirmed lineups hours ahead of time. Today I think it was the 5 o'clock hour that it came out. MLB lags way behind before finally publishing it. Because they suck, basically.
The lineups are not confirmed until they're physically handed to the HPU at home plate before the first pitch. Things get posted earlier all the time.
Sorry to bust your bubble but yes they are indeed confirmed. Of course something could come up at the last second and someone is scratched from the lineup. That happens from time to time. Please save yourself the trouble and don't argue the point any further. Because you sound like you're about to get into some ridiculously stupid semantic argument.
My point was nothing is official until it is handed to the ump. That's not an argument, it's just a correction.