The tantras can be very confusing for a person who is new to Buddhism, and for several thousand years the rule was not to expose a person or a new monk to the tantras until they had practiced for many, many years.
It's so silly. All you do is get the heck out of your body when you die. My gosh, everybody's done it thousands of times. Just because they don't remember, it doesn't mean they haven't done it.