The defaults are the same because they were never changed for sqlfire, which is built on top of gemfire. So, sqlfire just inherited gemfire's defaults. I haven't head of it being a common problem, certainly not in production environments for which we recommend that locators be used. In any case, it's a valid point--the default ports should be different between the two products.
The two products obviously cannot be mixed in the same distributed system, so if multicast is used the port has to be different, and if locators are used there have to be two sets of locators configured with two distinct sets of ports.