They are hardly copying Twitter in this regard. Twitter is doing it for fuck knows why, trying to get more money from a dieing platform or something. But Threads:

“Spam attacks have picked up,” requiring new rate limit changes.

Are mitigating spam. That is reasonable and any sane platform will have rate limits in place to stop abuse. They only question is if the rates are low enough to affect normal users or not.

So just because two companies do the same thing does not mean they are strictly copying each other, here they have different reasons as far as I can see.

If you are going to complain about something, do it for reasons that make sense. Don't make shit up.