I think those are the binaries. Opening those on nano/vim shows unreadable characters.

I mean, if you take a look at this page: https://benbridle.com/projects/bedrock/bedrock-pc.html

"To assemble a source code file program.brc and save the result as the program program.br, run the command..."

Where are the brc files?

Ah, you're right, I didn't see that.