Yep - Gill is simply wrong. The sheep and goats telling is NOT a parable.
Rather it is the telling of a literal reality in which two figures of speech are employed for the ease of each's use - as a "picture...worth a thousand words."
Matthew 25:32 And before him shall be gathered all nations: and he shall separate them one from another, AS A shepherd divideth his sheep from the goats:
It's a parable.
If it's not a parable, then an atheist with no faith at all will enter the kingdom if the atheist feeds the hungry, gives water to the thirsty, clothes the unclothed, invites a stranger into his house, takes care of sick people, and visits prisoners in jail.