Actually, Su Nian already had an answer to this question.

After all, the Frost Spell skill was also tied to his Basic Attacks. And he remembered that every time he used the spell, which was cast through a Basic Attack... his Talent would still stack!

In other words, although the Percentage Execute Talent required Basic Attacks to stack and trigger, as long as something was related to a Basic Attack—even a skill cast through one—it could still be stacked and triggered!

However, a character skill was one thing. An equipment skill might be different.