iCloud ADP and web access implications

Does anyone know the implications of enabling web access for iCloud when ADP is enabled? I’m trying to determine whether it decrypts client-side or if it just shares a key with the server and allows the server to decrypt select data. The info on Apple’s website was not super clear (it seemed to say it was done on the server, but it simultaneously said on another page that Apple cannot see the data with web access enabled), and I’ve found a lot of contradictory info online.

The usecase is setting up iCloud Drive through rclone.

Yes:

The latter:

That’s what I assumed. Unfortunate, but I guess I can just encrypt the data with rclone.