I’m not sure what you mean. Are you saying that St. Gregory of Nyssa and Origen did not actually mean to say that all souls in Hell would one day end up in Heaven, but just sound like they do because they are talking about purgatory, not Hell?
I read some of Gregory of Nyssa (if memory serves) and Origen that was wholly compatible with our notion of Purgatory as an anteroom of Heaven and Hell as another possibility. The heresy begins once you say that everyone ends up in Heaven. It is possible that they also said that, and sure that many understood theem that way, and therefore they came close or even fell into that heresy (Origen, at the least). But I am also saying that much of what they said was not stating that heretical thought and simply taught essentials of Purgatory without naming it. Origen, by the way, denied that he ever taught that Satan himself will eventually be pardoned. But if Hell never collapsed in his view, then it is Purgatory that he taught.
For example, if I were to say: “souls pay for their sins with suffering”, that is correct teaching. If I also say “God is so merciful that often he stops their suffering, forgives them and rewards them with Heaven”, that is also correct teaching, and that explains Purgatory. It is only if I replace “often” with “always” that I fall to origenism, because the possibility of Hell collapsed in my teaching.