wouldnt be any be any need to have the buy rounds so there would definitely be extra games
No, there is no reason to "buy" rounds.
You don't seem to have the slightest idea of scheduling.
The AFL (or any other league) can schedule any length of season and how many games it sees fit.
The AFL (or any other league) can schedule a complete bye or a split round, whatever they deem appropriate.
Just because an odd number league produces a bye every week doesn't mean much at all.