I think it’s completely fair that Monzo have ticked Better Payee Management off The Big List because they have done both things they said they would when they released the list.
Since they were working on so much other stuff, I think they only put things on the list which they felt were achievable. This looks like another problem with the Big List section headings making people think Monzo have finished improving that area (see iOS-Android parity).
Payee Management definitely needs to improve though - hopefully an overhaul is coming in the next month or so.