Unfortunately, this thread is about two entirely separate issues.
1. How the French lockkeepers operate their uniquely constructed locks.
2. Some idiots treating a UK two lock staircase as if it were a single lock.
On 1., I can fully understand that French stubbornness has led to their rather "bullish" treatment of boats in their charge, We do, after all, have the stubbornness of Napoleon to thank for the fact that half of the world drives on the opposite side of the road to the other half. Good luck to anyone who crosses those guys - and whatever you do, don't mention Agincourt......
On 2. , all we are looking at is a boater who is too lazy to go up a staircase properly. He obviously came across both locks empty (no way to easily open the middle gates otherwise), and rather than take the time to fill the top lock whilst he waited in the bottom one, he simply treated it as one big lock.
The Engineers/Navvies of old could have built a single 13ft drop lock, but chose instead to build two 6ft6ins as a staircase - to make it safer, and perhaps a little more comfortable. But hey, let's not do that!
And to argue that is is "OK" and not wasteful of water is typical of the "we know better" attitude displayed by some on here.
Yes, there are no bywashes on that lock, but there is a great big weir (the old lock) on one side, and I guarantee that a few thousand gallons found their way down there. And over the bottom gates too.
And the fool is so smug about it, he puts it on Youtube. Yeah, a good advert for boaters...........