Despite it being their software, they don't maintain this part. It'd be like saying Firefox is responsible for preventing fake bank websites from existing (this is ignoring how they also ship malware protection lists anymore to try and help). The Discover app is just a client where a distro supplies the software lists. On OpenSUSE it browses SUSE (and Flathub, if you add it.)
On Ubuntu it browses Ubuntu's APT repos and snap.
You can easily alter what repos the software uses too, it's just using whatever the distribution has configured it to use in conf files and repo lists.
Even the "thinking engine" ones are wild to watch in motion, if you ever turn on debugging. It's like watching someone substitute the autosuggest of your keyboard for what words appear in your head when trying to think through something. It just generates something and then generates again using THAT output (multiple times maybe involved for each step).
I watched one I installed locally for Home Assistant, as a test for various operations, just start repeating itself over and over to nearly everything before it just spat out something completely wrong.
Garbage engines.