Best would be a Sports Orthopedic, medical specialist, ergonomics analysis..
of course they need familiarity with cycling..

you done the Knee over pedal axis test?

crank at 3; &9:00, ie, level, plumb line from front of knee cap, front foot, falling through pedal axis.

part of a knowing fit by referring to numbers..

Thigh length changes , individuals are.. different. , ..

crank length and pushing the seat back & forth on its rails just part of the adjustments..

[I have too slow a computer to see the vid, anyhow.. ]