I saw this tweet, which is from April 16th, and the swords were released on May 2nd, which means they have a way to view assets before actually being released? May not be a bug with the website, but they definitely can get the meshes from the website somewhere.
It’s possible to make a program that brute-forces a bunch of assets and find ones made by ROBLOX.
Lots of people were criticizing the new ice crowns before they were released last winter