Never heard of this before. Why would I use this? I am assuming the messages are not actually encrypted, because on their own privacy page they state that they "process" messages and attachments sent through birdychat. So are they processing the raw unencrypted data on their servers or what?

From a cursory glance of their CSAE policy, combined with the above, it seems they would be very eager to comply with the dreaded "chat control".

https://www.birdy.chat/privacy