Truth b known hit the nail on the head. Without a belief in an immortal soul there is no resurrection, you are only a copy that believes its real. Its an unspoken and dirty little logical flaw in their teachings that few care to explore because the implications are horrifying.
As for their scriptural basis for this nonsense it amounts to some who saw Jesus resurected not reconizing him right away and this “teaching” or belief is not new. I was a kid in the 80’s and heard this.