So what other factors are there included in the 'Top Rating' calculation?

IRL the ratings of players are usually given in integers (or to half-integers, e.g. 8.5). The way of finding out who the best players are is to total all their ratings and divide by the number of matches they've played - which, up 'till now, this is how I thought that the 'Top Rated' table worked - recently a change had been made which restricted the table in the later part of the season to those players who had played 60% (?) of the possible games.

I can't recall anyone clamouring for any extra info, so why the change?

In computing we have an acronym, KISS (Keep It Simple, Stupid). Don't make this game more complicated than it needs to be...