in the episode before moltisanti died he told tony "that this is the second time paulie flaunted his authority to my face". moltisanti was a captain therefore the only way paulie would have authority over him is if he were the underboss
new york said "we think bobby baccalieri", them thinking bobby was underboss does not make it a fact. tony was grooming bobby to be christophers replacement that doesn't mean he was underboss yet
silvio gave the order to paulie that they were gonna hit phil and bobby give paulie the details. that doesn't mean he gave paulie the order, he gave him the details because tony told him to set the hit up
By the same token, Chris' comment doesn't even come close to making Paulie underboss. That's you reaching.
There's far more evidence to suggest Paulie was not underboss. There's virtually
nothing to suggest he was.