Another funny thing about Mac networking.

There's a game I play (Old School Runescape) that does network ticks every .6s. Mac does some sort of aggressive optimization on the network hardware/software, so network this infrequent doesn't keep the layers "hot", and you end up getting delayed ticks regularly, meaning you learn what should be happening in the game .2-.5s late. This optimization for (I assume) battery life makes the software not work as intended.

Playing anything that streams, like video, or triggering TCP connections (e.g. curl) at a more frequent clip while the game is running fixes the problem.

No way other than hacks that I've found to fix it, and I have no idea how you could report this to the right team at Apple to get it actually fixed.