Funny I know plenty of proficient musicians who can't read music at all. I don't disagree with what you are saying per sey but saying the creators can't be good musicians because they want to try a new approach to teach music feels awfully elitist.
The circle of fifth, musical modes and any advanced form of transposition, alongside the basic theory involved in cords, their components and their succession are necessary for a musician. [1]
Technical proficiency does not make you a musician, just like being able to type really well doesn't make you a programmer if you can't...read code.
[1]: This may not apply for percussionists, but even there, playing together with others necessitates the same understanding.
Side note: it's per se
That's pretty narrow. Some people aren't visual thinkers and don't need to see something on the written page to understand it. I personally know several musicians who have a deep understanding of music theory, but don't read music. You can explain and understand modes, transposition, chords, etc without having to write it down.
"don't" or "can't" read music? I think this is a critical distinction. If the answer is the latter I would still argue that they cannot have a deep understanding of music theory, since a major component of music theory is generally accepted to involve understanding notation.
Edit: I can accept that there are many aspects to music theory that go beyond just notation, but I am skeptical of 'deep understanding'.
That's not true at all. One can have a deep understanding of all the elements of music you mentioned without knowing any traditional notation. Maybe it's understood in terms of modular arithmetic and fractions and visualized as such, or visualized in terms of a piano or an abstract spiral structure or not even visualized at all. Traditional notation is only one possible representation (an a fairly arcane one at that); others are certainly possible and don't preclude deep understanding.
Tabs for guitar and bass are just one example of a deficient mode of notation, since they cannot provide all information necessary to play something.
If you want to forego all notation, however, understanding theory becomes even harder than with a deficient notation. For that, you'd have to solely rely on somebody's ear in order to explain roots, scales and afterwards more complex topics. The only other option is teaching visually, which ist somewhat possible with a guitar, and somewhat possible with a piano, but is not transferable to another instrument afterwards.
You are right that tablature by nature does not cover rhythm and that is a gap that won't even get you to muzak. However, there is nothing about classical music notation that makes it an ideal form for representing all forms of musical sound. How would you notate a Jay-Z or Skillrex song?
When I clicked this I was hoping for a notation that describes midi values against timbre (filters, distortion etc), and blends it with traditional notation, I think that is a missing link between old and new - but rewriting accepted notation for generations? That's like replacing a-Z with some sort of base 26 number and saying its easier to learn.
Dream on. You could show controller automation lanes as digital audio workstations do, but those are only as informative as they are consistent with some scheme like General MIDI and a standard sound architecture. Once you start resampling or using modular routings any kind of timbral notation schema goes out the window.
I've seen attempts at this, and if you email I'll try and dig you out a reference but the particular book I'm thinking of is in a box in my attic right now. However I can't say I've found them very informative. When I think about timbre I think about the whole synth architecture and program it in my head, for many timbral ideas it's just a matter of walking up to the synth later and dialing it in.
Most electronic musicians stick with simple diatonic scales or within modes, at most switching in and out of relative minor. Harmonic complexity and timbral complexity don't go very well together.
Edit: I do otherwise agree with you that a full musician should understand much of the theory of music, and not just be able to repeat a group of notes that they heard (that is, they should be more than just a human tape recorder).
That attitude makes you an ass. That might be blunt, but it's true. I can't imagine someone who is actually musical thinking that for even a second.