Returning false would make it break, and not read the next line with recv_line(pool), I don't know the code enough to guess if that means it would skip some valid stratum commands.
All in all I like your solution, gotta love opensource software, just because of situations like this.
You're right. In fact, I made it even simpler by just commenting out line 1686
//pool->stratum_url = pool->sockaddr_url;
This is the line that assigns the new pool url.