It seems like there are several verbs that have both deponent and non-deponent forms and they coincidentally are defective. So, for example, there is patio which has a deponent patior meaning the same thing, and imito also having the identical deponent imitor. Both patio and imito are defective in that they have no perfect tenses. Another example is runco / runcor.
So, what is the pattern here? Why do the words patio and imito even exist? If there are full-fledged deponents that mean the same thing and have perfect forms (patior, passus sum), why are we even bothering to have a defective form like patio? In fact, why is it defective?