Nope, neither of those things indicate that it is a polymorph effect - it has to either be based off of a polymorph spell or specifically say so.
In fact, the polymorph subschool section describes how polymorph effects interact with both size changes and abilities that grant natural weapons.
Polymorph wrote:
While under the effects of a polymorph spell, you lose all extraordinary and supernatural abilities that depend on your original form (such as keen senses, scent, and darkvision), as well as any natural attacks and movement types possessed by your original form. You also lose any class features that depend upon form, but those that allow you to add features (such as sorcerers that can grow claws) still function. While most of these should be obvious, the GM is the final arbiter of what abilities depend on form and are lost when a new form is assumed. Your new form might restore a number of these abilities if they are possessed by the new form.
You can only be affected by one polymorph spell at a time. If a new polymorph spell is cast on you (or you activate a polymorph effect, such as wild shape), you can decide whether or not to allow it to affect you, taking the place of the old spell. In addition, other spells that change your size have no effect on you while you are under the effects of a polymorph spell.
So Gift of Claw and Horn stacks quite nicely with polymorph spells, particularly because you can choose what natural weapon you get so that it doesn't overlap with what your form already has.
