🤔 Mine is testflight version FYI. 
Discussion
I know why.
The icon Blowater uses is defined by https://github.com/nostr-protocol/nips/blob/master/11.md#icon
Most relays don't set it. Instead, they set a favicon.ico in their HTTP server.
Such as https://yabu.me/favicon.ico
OK, I see (that there IS a reason which I don't understand.) 😅 Thanks.