I've been through 3-4 Atebus shop RSes and each time there's NOTHING new that RSes XS What gives?

This is kinda how all restocking shops work though? The higher the rarity, the less of them restock.

Also they just came out like, two days ago.

I would also add that they may very well have restocked, only you didn't see them because someone was already in the shop and buying at the time the restock happened.