weapons that list that they come with smartlink have an internal smartlink. weapons that list that they come with a laser sight have an internal laser sight. weapons that list that they come with a silencer or sound suppressor come with an internal silencer or sound suppressor. if you want an external accessory then you can buy that one the side.
yes, a few guns probably even state the obvious that the smartgun is indeed internal. Some guns probably state that the smartgun is instead built-in, which is the same thing as internal. this does not in any way shape or form make the rest external by elimination. this only mean that some guns have redundant fluff information that the other guns does not have. they didn't need to state that the smartgun is internal and they could state that the smartgun is internal on all other weapons - but that would not be the first example where the author(s) don't copy paste the same phrase.
i will be very surprised if you can find a weapon that include a smartgun that explict state that it is an external smartgun. and if the smartgun is external then it should explicit state if it take the top or the underbarrel mount (or are you suggesting that people that buy the pistol are expected to do an armorer + logic (4, 1 hour) extended test to attach it themselves??). If you can point us to any gun that come with an external smartgun then you might have a case to start argue... but until then, good luck mate.
+1 for internal.