Do you know of any tutorials that follow this "deep dive first" approach? That's exactly how I like to learn.
For example, this chapter: http://david.rothlis.net/emacs/customize_c.html
walks you through this example: What command is run when I press TAB? How do I find out? How do I find its (elisp) source code? How do I find the documentation for built-in elisp functions or macros or "special forms"? All culminating in figuring out (from the elisp source code) which variable you can set to customise your indentation level.
I wouldn't say never learn two things at once, but I'd be aware of the extra mental load you're creating for yourself. It definitely makes things more challenging.