The whole point of vibrato is to improve the tone of your violin. You won't achieve that by starting slow and speeding up. You have to start fast, listening for the tone created, then, when you have mastered that, slow down and aim for similar effects.

There are so many methodological/interpretative pitfalls here.

Two things: - 1) real slow-mo; 2) imagined slow-mo (avoid this like the plague)

Real slow-mo may show you an effect, but it won't necessarily tell you anything about the cause (which is what you seek).

If you looked at slow-mo of a long-jumper, you wouldn't learn how to long jump from it. You'd see flailing limbs and bouncing jowls and slabbering chops. You wouldn't emulate those in an attempt to get it right. They are just effects of long-jumping.

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The angle your finger makes to the string depends on the string and the finger and the position. You can't practise all those individually using different slow-mo analyses.

Like I have said elewhere, play the violin like a guitar or a banjo for a few minutes. This requires a different approach to vibrato and one which will be geometrically correct for a lot of the variants.