Thank you for sharing your own experience. When you selected Model Y and 2017-2022 Model 3, did you get a warning that the product was incompatible with your vehicle?
In any event, please let us know after your 5/5 appointment, so I can let my dad know.
You should ask your dad to go back to the Tesla online store now and try to order homelink from his account now, and see if it still says its not compatible. I am going to guess that his response would likely be "it doesnt say that now... strange".