It doesn't help us immediately... but it tells us something later on after we get more facts to analyze.
This is only the 2nd day and we've already had 3 role claims. Normally, to prove a claim, someone just needs to volunteer their invest subject before and confirm the result after -- and we have protection to cover them so the mafia hit would fail. Without Lab Rat, we can no longer protect the real det now or later. That means the mafia gets to kill whomever it is tonight.
As it stands now, we can all come up with umpteen reasons to believe or disbelieve either one of them. If we (collectively) guess wrong and lynch our own detective by mistake, we've just handed the scum an additional hit they don't already have.
Whoever Piranha and Rich tell us they intend to investigate won't be proved right all by itself with only tonight's nightfall result. But it forces the mafia to kill the real detective now using up their hit instead of our lynch because we won't already be killing the person for them.
Then, whoever is named as the intended invest by Pir and Rich (before one of them survives the lynch and the hit)... that person will at least know whether the surviving claimant was lying or not. That gives us useful input from at least one other townie or more rope to hang another mafia member later in the game.
This is still real early in the game and nothing we do will give us the whole picture. We're still gathering little pieces to the puzzle.
I just don't see any value in potentially killing our own det accidentally. We should make the mafia use up one of their hits instead to do that themselves.
