Probably to improve performance cost/system strain.
Why not then just state in patch notes, that this was the reason. I don't personally agree with reducing player count in push. There are other game modes where reducing player count might make sense.
just speculation, but I can't see a tactical reason for reducing player count on such large maps. I mean Rising Storm 2 Vietnam have 64 players and that does not make it less tactical. Why would more players reduce the tactical aspect, it makes no sense right? What it will reduce for sure is strain on system and there is definitely not going smooth performance wise for many players. I would also prefer even more players, its both fun and difficult with many players as the game gets more complex. Guess it depends on what they mean by tactical, it would be tactical to let players play without stuttering;) Would probably not look cool to write in the change log that the current game can't handle the amount of players, as similar games does it without any problem.