They like cloudflare? I’ve never had to verify with it

They use it. Everything you upload is run through either Cloudflare's or MS's CSAM scanning. Everything. Wtf do you think CF and MS is doing with YOUR media? To be fair, NB is totally up front about this. They do not hide it at all. But... I refuse to use their services except in very rare and specific cases.

Nostr.build isn't Nostr, it's an HTTP cloud storage service with "nostr" in the name.

It's a huge part of what makes nostr nostr. It's other stuff. You also sign events with your keys. You do realise the relays (the R in nostr) are just servers, right?