I wonder which is the cause, and which is the effect. In other words, perhaps the inhibition of PKR acts first to increase anxiety; and it is this which causes a side effect of memory enhancement.
WRT your first sentence, "According to ... , memory is the inability to forget." I read a brief biography of a memory savant, 19th century, don't remember his name, who affirmed that he never forgot anything that he read, or saw, or heard; and he was a very unhappy man. Almost everything he looked at served to trigger (involuntarily) dozens and dozens of facts and visual memories, of related stuff. Got in the way of his enjoying the moment, I suppose.