I helped my high school friend try to get the engine back on the transmission after he had reassembled it. However, we never got it running as we could not figure out how to get the splines aligned so the engine would actually engage the transmission. We (mostly me) had no idea what we were doing.
So to see these guys do it in under a minute is embarrassing to say the least. It took most of an afternoon with no good result.
a) These guys aren’t just mechanics. They’re from a family business that was (one of?) the first Volkswagen mechanic shops in Australia. The shop hung out the “Volkswagen Maintenance and Repair” sign in the 1950s, which puts them solidly in the “before it was cool” camp. So the people in this video don’t just do VW engines as part of their job - they were born into handling VW engines like farm kids are born into farm work.
To be fair, they didn’t do anything that might change the position of the splines so didn’t have that problem.
If you don’t know the procedure then taking it slowly is always the best policy with any mechanical job (found out through bull-at-a-gate tactics that failed).
A friend had to work on her dryer, and wisely took photos of each step as she dis- and re-assembled it, comparing each one to the tutorial vid she was using.