They took the code of Scratch 3 and claim to have made some improvements on it to make it run faster alongside some other improvements (such as rising the maximum framerate to 60 from Scratch’s 30). However, there doesn’t seem to be any proof that this is the case, so it could perform exactly like Scratch 3 without any improvements.

What is an actual bonus is that this software offers actual installation files, whereas normal Scratch 3 is only available through a browser and by downloading it from the App/Play/Windows store. It’s nice to be able to not use these storefronts because a) it means that you have a little more control over the software you use and b) you can use Scratch 3 offline on Linux as well with this.