Yes, but do you know any writers--great or not--who don't know the alphabet?
Looking for conformation of such a fact is what holds learning back, how about looking at the number of people with....say dyslexia that cannot use the alphabet but have still had success?
To what degree do you have to know the alphabet?
Do you need to recite it backwards?
Do you need to know every other letter?
Do you need to know what letter only cover the teens?
Do you need to recite every other letter backwards that only appear in the teens?
All the above is over thought out, it is time wasted and nonsense to suggest a writer will be any better for doing it.
Music can be the same, working on ideas that are pointless and meaningless because they seem good or offer some in-sight into a new dawn can be for most a waste of their efforts.
Understanding the ideas and information being presented is the first lesson, then how it can be applied is the second.
Some ideas are taken on a leap of faith, and even though learned some ideas are not fully taken in, they are not questioned or examined to much because that leads away from the original lesson premise.
Staying in the moment of a lesson and idea is where a teacher comes in...it is called focus.
Anyone looking for musical ideas or find scales boring are out of that moment, so it will take them longer to learn to learn what they should be working on, which would be understanding scale construction and playing them.
It is usually the student that come to me and tell me they found this line or that line that sound like this part or that part of a scale. As they continue they find more and more relations to music through the foundations they build.
I had a new student a few months ago, his parents brought him along to the studio, we worked for two hrs on setting him up, getting to know what he expects from lessons, and me telling him what I expect from him.
He took away a lot of homework and sheets with the principals of scale construction,triads,arps., fingerings etc. plus links to info on my web site to work on.
His parents asked what time next week and looked shocked when I said it would be 8-10 weeks before he needs to come back. I explained that bring him back next week and they will pay me to cover the same ground we covered today.
They will pay me to watch him practice, not pay me to teach him.
Once he has the physical skills down to play what I teach him then he may come back sooner and sooner, and maybe even every week if he so desires.
For him the lessons are meaningless until he can physically play what is being taught, all lessons will become to him is frustration, a doubt of his abilities, and ultimately a chore rather than an education....then he loses interest.
I know from talking to him what he expects, so I know he will be back, but I suspect his parents will take him somewhere else where they can pay someone to watch him practice and feel they are getting value for money because he can play songs rather than learn how to create them.
Scales give the physical work out that the fingers need, no note is more that a fret away, you use all fingers to fret them, you need stamina and dexterity to play them, and because you have stamina and dexterity you can hold a tempo without tiring, so your timing is better....because you can move from note to note across strings, your timing is better.
Hesitating or being un-sure what to play next or struggling to play what is next, or get in a position to play what is next will lead to timing issues that no metronome will ever cure.
Never mind the theory benefits of working scales when a student starts, the physical side is what will get them every time.....they just cannot physically play...that is the first barrier they have to get over. When they tire they should then they read a little bit,drink some water a little food, this gives the hands a chance to recover and re-fuel,then they play... rest.....read, then play etc.
Eventually the need for rest diminishes and then they can play, then they are ready to learn and as such they are ready to teach. There is now a foundation to build on and musical ideas to be explored and that takes a life time that lessons can prepare them for.