The video posted is obviously a test on the side of a high rise building that may have been built to practice fire-fighting. I think it was filmed in central China.
That said, the lifting ability of those drones is impressive. Water hoses are heavy!
What you say makes sense. But as you pointed out - it’s the lifting power of the drones that is quite something. If I find something else on them online I’ll post it here!
Chongqing it seems. You’re right. Here’s the youtube clip. Big octocopters with vast batteries that I doubt many could afford!
The hose attached to these drones is very thin and light. Watch carefully the spray from the nozzle in the second video. Rather than water, it may be some kind of fire-extinguishing chemical or powder, such as that used in many of the extinguishers you buy in the shops. And as they are captive drones, it is likely that they have a power feed cable from the ground.
If it was a substantial jet of water, the reactive force would powerfully drive the drones backwards.