I grew up in Hong Kong and way back in the early 90s, if you hit the MTR (the underground/metro/subway system) turnstile hard enough with your thigh as you were walking through, it would give way, so you could basically travel for free. No jumping required, which might explain your observation!

I think they've changed them now, and I think it only ever applied to the turnstiles on the Kowloon side of the line.