As you say: “couldn’t be improved upon”. This is philosophical and inaccurate. The question is, what exactly is missing in terms of understanding? If all vipallasa about anicca/anatta are removed, what is left to do?
Is there a lack of panna in general? Or is there only a lack of panna regarding dukkha and asubha? That would have to be found out by means of tipitaka and commentaries.