I already messaged David. Just posting this so anyone else can add in anything else.
In Magi of Hermes, p.101 the spell "Arachne's Tuition" has at least two issues.
It uses the Base 4 "Control the large-scale physical movements of a target" and functions like the Base 10 "Control a target's motions". Only having control of large-scale movements would not allow "particularly complex task". [EDIT: The spell is designed by a weaver and its flavor text talks about teaching weaving. That is fine movement of the fingers.]
It uses Range: Eye which would totally interfere with its intended function. For the Caster to have control they would have to be looking the Target in the eye (as per ArM5, p.111). It is kinda hard to direct someone through a complex task or show them how to do something while the two of you are staring each other in the eye rather than looking at what you are doing.
The Range becomes even more of a pain for changing commands after eye contact is broken since you are going to have to grab the Target by the head and force them to look you in the eye.
Moment I looked at that spell I went "Nope". With all the reviewing we have been doing we are getting predisposed to look for errors and that one was a "how it functions" one so glaring to us at this point.
"A spell that has a continuing effect remains in effect even if the caster moves out of range." It's not a necessity to keep staring in the eyes throughout the spell. It's a range, not a duration.
Yes but once you are no longer looking them in the eye you lose control. If you were just doing something like "walk over there" that is fine. Directing someone through a complex action where you maintain control in an attempt to teach them via muscle memory however pretty much requires you to maintain control the whole time.
EDIT: This is why Touch works and Eye doesn't. You can stand next to them with your hand on them to maintain control and make them do the action while you both can look at what you are working on. Maintaining control with Eye involves staring into each others eyes.