Many Scuba skills are perishable. This isn't a hard lesson to teach, and in fact it's fun. Us instructors love to make you think outside the box and be ready for most contingencies. You had it down pat when you first got certified and then you bought all that new gear. Years later, the overlooked inflator finally decides to stick open. Are you ready? Will you remember what to do? You've cleared your mask any number of times, checked gauges, kept off of the reef and many, many more skills that make you a diver. But, it doesn't take long before muscle memory turns into mental mush if you don't practice all the basic skills. It's easy to blame the instructor for anything and everything that happens. Hell there's an entire industry based on shifting the blame from the person who made the mistake to someone who wasn't even there. That doesn't help when the caca is hitting the fanola.
I can teach you to dive. I can't make you stay sharp. I can't make you do it the way I taught you. I can't make you remember. I can set the example, but will you follow it? If you want to be a competent Scuba diver, you'll just have to take the onus and be one. It's really not that hard, but it's entirely up to you.
Ah Ha, I see the muscle memory term is alive again! Boy this term really has legs. Practice until it becomes ingrained and also getting something that helps in facilitating this procedure like the (DSS LP hose release flanges) is really a good idea.