caranthir: The drawback with O2P1L1 is precisely that it leaves that said atari behind for no gain at all, something which w can use to make a sente seki (that would be gote in the accepted solution) either immediately or later, or as a free ko threat.
semelis: After b O2, w P1, b L1 black is alive in seki if white ataris at N1 or with 2 eyes in any other case, but is marked incorrect.
Other problems mark both seki or 2 eyes correct to live.
The drawback with O2 P1 L1 is precisely that it leaves that said atari behind for no gain at all, something which w can use to make a sente seki (that would be gote in the accepted solution) either immediately or later, or as a free ko threat.