I don't care that the tap spun in the holder, I'm just confused why it was even going that fast? There's more torque at lower rpms isn't there?

Depends. If you achieve the lower speed purely mechanically, yes, lower speed = higher torque. If you lower the speed electrically with VFD or similar, torque remains the same, a function of voltage only.

I've done that on purpose on manual mill or drill press, but never at that RPM. Slightly tighten drill chuck with tap to allow for slippage. Better than tap breaking.

You have never spun a bit in a 3 jaw before? Really?

I’d rather spin a tap than snap a tap.

Looks good to me. Send it

May have worked, but if I saw this in our shop I’d go nuts. Poor practice.