I have many Pis at my home, and all of them can connect through samba, although I don't force any min protocol version. Windows 10 and Android latest versions also work fine. It may depend of which versions of samba you are running, mines all running Raspbian, same samba version. Which exact OS and samba versions are you running in the 2 Pies?
PS: Don't know why are you exactly forcing SMB3 protocol, samba is a flawed protocol, no matter which version, it is not hard to crack.