The video emphasizes getting comfortable underwater as cruciaI, and how that may not happen in a 2-day class for many candidates.
That is absolutely crucial, and it won't happen in a 2-day class. I'd say it won't happen for anyone.
There are frequently questions on here from people who aren't strong swimmers that want to get into scuba diving. The responses usually say the two are different, but a strong swimming background will definitely help.
I was around water pretty much as far back as I can remember. I vaguely remember when my parent's put in an above ground pool, and I can more clearly remember when they changed it to inground. My parents put us through swimming lessons as early as possible back in those days. As a result, I was always very comfortable in the water. Never had any issues at all with my OW training, and being able to do the skills necessary. My first OW training was a joke, but that's only because they only required me to do a single dive. Not nearly enough time to practice.
When my kids were born, they were exposed to water very early. They started survival lessons at around 6-8 months old. Now they are 8 and 11, and both are quite comfortable in the water. The 11 year old is a certified diver. I was permitted to go along on her checkout dives after her pool sessions. She did well on her pool sessions, and was comfortable in the water. She was way ahead of most of the other students during the pool sessions. During the first checkout dives, they did do a bit of kneeling to go over the drills (mask clearing, regulator recovery, etc.). While they were doing that, I got to wondering if the students would really remember what to do if they needed to do a regulator recovery in real-life.
After all, it's one thing to do it on command where you can prepare for it, and it's quite another thing to do it out of necessity. So, I was wondering if my daughter would really be able to handle herself if she loses her 2nd stage for some reason. On the 1st dive the next day, she answered that question. While swimming, another student accidentally kicked her, and knocked her regulator out of her mouth. It immediately went behind her in free-flow mode. She swept and reached for it, and when she didn't immediately come up with it, she grabbed her backup, cleared and started breathing. By that time, I was there and was able to get her primary under control. Maybe not a textbook recovery as she didn't immediately come up with it, but there was no indication that she was ready to bolt for the surface or anything like that. She did what she needed to do at the time to continue breathing.