Because that Mosquito is from 418 Squadron RCAF, still made in England
It is just because it is an old model which is long overdue an update/debugging. I am very surprised it has not ever had a going over since it was released all those years ago.
HTC made some curious aircraft choices in their early days (no dig intended), it has changed now though. Remember the hybrid Spitfire IX? The Seafire we have which is pretty much the rarest possible? The uber late Spitfire V? The Lanc with .50's in the tail? Then there are the BoB era aircraft which make the BoB scenario pretty pointless. The late war Stuka, un-interceptable Ju-88, insignificant 110C-4.
I think it is something to do with the available data at the time. And HTC had no concrete stats of Mossies without flame dampeners.