Wrong. With the pedal at the bottom of its stroke the leg should be in what's called the "naturally cocked" position, meaning hanging loose rather than stretched straight. In this position the heel should just contact the pedal when swung gently back and forth.
This thread contains some of the worst advice I've ever seen collected together in one CC thread.
FWIW the hip movement in the OP's video doesn't look abnormal to me. What you're seeing is the muscles moving. A video shot properly in landscape (hence taking up the entire screen) with the rider's hip area in lycra shorts and top or even just underpants and bare top would tell us more. There will always be hip movement when making an effort so in the landscape video, ride with normal effort.
I said 'straight', not 'stretched out'! What is the effective difference between just contacting the pedal and the heel being on the pedal with the leg straight? A few mm!
I'm not sure you fully understand what rule of thumb means (
a broadly accurate guide or principle, based on practice rather than theory). There is no one size fits all 100% correct measurement for the saddle height/leg to be and there will be slight differences for riders based on physiology and history of injuries/knee problems, and possibly type of riding. As such, I am pleased to tell you that your rule of thumb for correct saddle height is OK as well.
Once a rider has got a saddle height by whichever rule of thumb they choose it will usually need a few minor tweaks following practice before it is completely right for them.
Disclaimer: I am not a professional bike fit practitioner, nor a professional physiologist/physiotherapist. So my views are just as likely as other people who are not to be bollux.
