I don’t believe this site/tool/product is permitted under the TOS/Bits Acceptable Use policy.
https://www.twitch.tv/p/en/legal/bits-acceptable-use/ but I’m not a laywer.
Looks like, according to their FAQ, that if you use bits in their channel it’ll assign another currency, and that currency can be used on the site.
So they are just using the cheer eventsub or pubsub topics to consume bits usage events.