But wait, there's more, we're standardizing our Groups implementation so other projects can take advantage of our App and Client API.
So its compatible with lemmy but uses a different API and they want their API to be the standard for the threadiverse? This is why we should be using the C2S, but since we're not you should just stick with the lemmy api since that's where the client ecosystem is already at.
Update on Pixelfed groups (mastodon.social)
Shipping soon ™ but we heard that before. Still looking forward to it and they explicitly mention Lemmy compatibility....