I am happy enough with the ones I linked and don't question the standard of the unit produce.
But jacking up a car with a hydraulic jack and the hinging type axle stands would not be the safest thing to do if the ground has any undulations at all.
I often have to realign my axle stands as they twist off plumb when jacking up the car. I would guess (don't know) that the hinges might hide some of the missalignment which then increase the chance of the car dropping off the stand(s).
Quandry please ignore the fact that I tried to make a car land on me in Cork while removing a gearbox with a bolt still attached. I know Agusto and you could have lifted it of my cold dead body