This is a classic case of
lifting drive
versus
Sinking drive!
Best demonstrated against chop
In lifting drive the ball is brushed vertically and has a high arc and therefore kicks high
In sinking drive the ball is brushed more forward over the top and so tends to dive toward the floor...
though yr 2nd clip illustrates well what we are talking about your suggestion that it shows the amount of spin generated as stabilising after 3 reps as a bit subjective. Yr ball striking is not near enough to a pure brushing motion to be a good test. In an (equally subjective i admit) practice...
wrong
consider 2 identical robots infinitely playing identical backspin strokes to each other (1st stroke struck from hand)
consider ball/bat impact speed which will effect the spin
1st chop has impact speed consistent with stroke effort x + zero rotational force from ball
2nd chop has...