http://urheiluuutiset.com/rallin-mm-...ensi-kaudella/

This one has thinked it like this

WRC2 = all current WRC2PRO and WRC2 drivers (5+13 cars in Wales)

WRC3 = all other R5 drivers which are entered to event (now in Wales 7 cars)

so basically if you drive with R5 you are either WRC2 or WRC3 driver.