Short answer: it's not just your kiddo :) The good news is...after many, many, many repetitions it may take only a small prompt to recover the info ;) One piece of advice....keep it simple. repeat it often. have them repeat it back to you..........wait a few minutes....ask again. But above all: always remember the KISS rule ;) Keep It Simple Silly :) The fewer the words the better. ;)Oh and specify! Our kiddo's need clear cues.

Unlike our NT son, our ASD son has an excellent short term and working memory (especially verbal memory). He lacks long attention span but that is different issue. All kids are different here.

Not just your kiddo. Mine couldn't even form memories properly for a long time. They would form partially, out of order, opposite, etc. Look up "executive function disorder."

My grandson is the opposite. He memorises dialogue after one hearing and repeats it back. Songs, too, in a well-pitched choirboy voice (he's 14). On the other hand, he doesn't always know what he's saying, and says\acts out inappropriate phrases. Just now, he's beginning to understand the latter. "I'm not being inappropriate today," is often heard.
He has fixated on "Toy Story" since age 6 months. The mutant toys fascinate him. Someone printed a photo of said toys which he carries everywhere. With this, he recites everything he knows about each toy; can't stop until he's covered them all.
From "The Incredibles", he fixated on "Bob" pre-superhero, and deliberately put on weight to look like Mr. Incredible.
Other concerns: poops his pants & isn't deterred by smell or discomfort. He has run away, getting lost in the woods at age 8, then along the highway at age 12. Once he ventured into the street to experience getting hit by a truck. Fortunately this was avoided, but he still doesn't understand the dangers of vehicles v. pedestrians.
Bright side - adores his little sister (5 years difference), is gentle & affectionate with animals, from my cats to a toad that visits at night, says "I love you" reflexivley, can make his own meals using the microwave, spells beautifully, is adept on the internet, whether computer or smartphone....I'm sure there is more. I only have him one day@week.
Elijah was born at home (2nd generation) without complications. We have a religious objection to vaccinations, so we know he did not develop autism from the ingredients therein. I raised him til age 2 so his mom could finish school. Giving him over was heartbreaking, but my daughter has done an incredible job raising him. We have experienced meltdowns, hitting, and touching of female relatives. Most have been brought under control using enormous patience and love. He's in regular junior high, but not mainstreamed. Math is a complete mystery. He prefers verbal learning thru headphones, I think because headphones shut out distractions.
Q. Are prominent teeth a commonality? He needs braces, but he's much too scared and hyper to sit in a dentist's chair.

If a picture/something visual can be used as symbol or representation, it can really help. Many ASD children are more visual learners. It's been working well with my 14yo son.