Is that a problem in practice, though? If I were conducting a count under a cardinal voting system (such as range voting or approval voting) I would count one c

Is that a problem in practice, though? If I were conducting a count under a cardinal voting system (such as range voting or approval voting) I would count one candidate after another. This would really slow down a count involving a large number of candidates, which is bad for a system aiming to increase voter choice. However, under IRV/RCV I would literally put the ballot papers in piles (one for each candidate) and count each pile. It's possible (and, I believe, typical) that less counting is required under IRV/RCV than under any of the other voting systems mentioned on the page you linked to (with the exception of plurality voting).