I agree with you but if you look at it on the other side, the smaller teams are trying to make a statement and they can't do that if is not PSG they're playing against and the PSG in question have a way of letting the smaller teams to humiliate them before you see them start struggling to gain dominance. This game between Len and PSG was suppose to end at FT without going to Penalty shootout but PSG as we know them don't know when to act as the bigger team in these domestic competition, how I wish Lens was a bit stronger than what we saw to eliminate PSG from the competition.
Normally, there's this morale booster these smaller teams get when they're able to beat the bigger teams and if Lens had been successful in removing PSG from the tournament, it would have pushed them to feel like they can beat them in the league and knowing how PSG can be shaky in their playing pattern like you observed, I don't think it would be a difficult thing for them to do.
With how careless they played with Lens but we're lucky thanks to the penalty shootout, I doubt if PSG would be able to survive if they meet a bigger and stronger opponent in the next round.