Yeah, this episode seems clear enough, given King's right to fictional license. Both Schrödinger's Gunslinger and his boy have what amount to split personalities, which King certainly spends enough time describing, presumably brought on by the original incident in The Gunslinger when Roland abandons Jake. It's driving them nuts, and they are both cured when Jake is pulled through the door into Roland's world. But nothing it said about memory, so we may believe that Jake remembers the events of both tracks of the "split" period.