You can be certain that diverted passengers are counted - if they disembark and walk through the terminal and get on busses to Dublin, Knock or Cork those passengers are terminal passengers.
To be fair that is reasonable.
What is not fair is how Cork originating passengers whom stayed on the EI aircraft as passengers bound for Frankfurt some years ago were counted not as transit passengers but as terminal passengers at Dublin.
Unsolicited info came my way to that effect - now, whether it was by EI or Aer Rianta I do not know so as was said some posts back on this thread who can you believe and waiting for CSO figures is only as good as what is recorded and how it is done.
Whom can be believed - there are lies, damn lies, and statistics!!