Those four spoke 10 1/4″ wheels, introduced on early Mk IX’s, are actually correct for the Mk 21. LA255 was so fitted for all its time at Cardington.
CAACU 21’s seem to favour the three spoke 12″ wheel and brake but most other users of the type seem to be fitted with the smaller units.
Even the mighty Seafire 47 reduced from 13″ back to the 10 1/4″ post production. Too many pecked propellers I suspect.
Mark