I disagree strongly with this, it's like saying you must understand the subtleties of calligraphy or typography in order to be proficient at writing in your notebook with a pencil. I have no doubt you will be more purposeful and deft with your handwriting having this knowledge but they're two completely different skills.

You can be taught to and be proficient in "writing with your pencil" by learning the rules [1]. Efficient, practical, immediately useful and applicable. No subtlety required nor desired. It's the same as all practical skills or trades.

[1] https://stylepedia.net/style/

Style guides can’t teach you what not to write. If you can’t see what could be missing, how do you know you’re making any sense?

Holding yourself to a standard doesn’t mean it’s a meaningful one.

I just used that as an example because it's free, high quality, a good reference, and goes beyond what you would expect out of a style guide and is closer to a textbook on technical writing. So just replace it with your preferred technical writing manual—although a lot of them tend to call themselves style guides or manuals of style.

Either way, it's an avenue of learning to write that ignores, I would say, all the artistic aspects of writing. Inasmuch as you can say anything "isn't an art."

I believe you are confusing verbosity with artistry, and ability with precision. A good writer knows when to smother their creation.