Except that when it's a gerund it's not a verb anymore. It's a noun.

I meant differentiating the gerund from the present participle. In English they are identical, and since there's already a more general rule that says nouns can be "derived" from adjectives by zero morphology, I, personally, see no reason to multiple forms. We just call it a gerund because that's the term used in Latin grammar.

Ceci n'est pas un seing.