Exposing for the shadows protects against underexposure, especially in contrasty scenes. It's just a way to meter that happens to work out well for almost all situations. It's not the Zone System. It works well with today's materials as long as you have a standard development time that lets you print very flat and very contrasty scenes well.
(Note: exposing for a midtone or highlight and then compensating in contrasty situations by adding exposure when the meter would otherwise underexpose works just about as well, maybe not quite as precise, but...)
"Exposing for the shadows and developing for the highlights" is the exposure part of the Zone System that was developed for materials of yesteryear when achieving a negative with overall density range tailored to mid-grade paper was desirable. It entails measuring the subject luminance range of the scene and adjusting development to achieve a highlight density that is about the same in all cases. (The Zone System uses one-stop Zones for development changes, hence N+1, N-1 etc.)
Using your meter to evaluate the luminances in a scene, being able to distill from that information the expressive possibilities available in that scene, having a concept of what you want to communicate and how that can be best translated visually into a photograph and then exposing and developing to get a result that matches your visualization and intent, that is using the Zone System (including the use of filters, intentionally over- or underexposing, expanding local contrast at the expense of overall density range making for a difficult negative to print, but one that results in the print you want, etc., etc.,) Really, it's all about visualization. Anyone can expose and develop properly with a bit of practice and understanding.
And, since the Zone System is a simplification of the science of tone reproduction, you can go beyond it once you've become comfortable with it, and modify it as needed for your particular situation and today's materials. For example, there's less of a need to alter development to achieve a standard density range on the negative these days. Both films and papers allow greater latitude. So, one can dispense with extreme contractions or expansion developments and their inherent shortcomings and use other contrast controls and techniques (e.g., split-grade printing) to obtain even better prints than were possible in the past in some cases. Or, one can do the opposite (Phil Davis) and make negatives that all print really well on one grade of long-out-of-production Azo, or some alternative process, or scanning.
How deep one wants or needs to go down the tone reproduction rabbit hole depends on lots of things. The Zone System is just one practical application. What sets it apart from many other systems is it's emphasis on visualizing results based on evaluating luminances in the scene. Unless you're doing that, you aren't using the Zone System.
Best,
Doremus