Maybe you have a very different idea of what “music theory” is than me but I don’t believe you can learn it in 20 minutes. If by music theory you mean major and minors scales and their diatonic chords then sure, you could learn that in 20 minutes and it would help your music. To me at least, learning music theory is more like learning a language and those basic scales and chords are like spending 20 minutes with an Italian phrase book and then claiming you can speak Italian. I don’t think Jaron was trying to convince people to stagnate, rather he was saying that you shouldn’t feel like you need to learn every word, idiom, and grammatical rule of Italian before you try speaking it. Instead try to learn a single new concept at a time and spend time working into your practice and see how it fits with the concepts you already know well.

you are extrapolating quite a bit here, theres plenty of ways to think about what 'one thing' could mean here. if that one thing is a concept like say odd time signatures, you would not be stagnant for spending a year exploring that... you could do it for a life time and still discover something new every now and then. the main point however is to prioritize things you actually find interesting and actually get started doing something rather than feel overwhelmed and paralyzed. this creates a positive feedback loop that in most cases will lead to people realizing that it can be fun and exciting to learn more instead of using up your discipline learning about things that don't really directly relate to the music YOU like. and no you cannot learn the entirety of music theory in 20 minutes.

It takes twenty minutes to learn theory top to bottom, everything you’ll ever use as a songwriter or musician. You’re overcomplicating it.