No, this was true for IOS back when I studied for my CCIE. Doing a quick google search, I found this interesting article
. Apparently this rule is implied in RFC 4271. The FRR developers confirmed that we certainly enforce this, but it can be turned off. If you think about it in a "real world" topology, would you really want to peer BGP using a default (the least specific route)? Glad it is working!
Thanks Jason. Now that you mention it, I do remember having a specific route, vaguely. Been several years. Makes sense. Thank you so much.