Where to find the CSS styles behind a Salesforce CSS class?

Background

The Lightning Design System shows the CSS classes you can use for a finite number of scenarios.

The problem

I don’t like this. I prefer being able to understand what is actually being applied and what specific classes are doing. I’ve found that several scenarios provide me the same exact appearance when I remove one of the classes in the Lightning Design System example. This makes me think the CSS I’m adding is not minimalistic.

For example, what if a complicated Salesforce CSS class has everything I want EXCEPT one style makes it unusuable for my use-case.

Some speculation

Is Salesforce intentionally hiding the styles being applied? You can use Browser tools to inspect, but that can be tedious.

Is the general expectation that the developer uses Browser HTML/CSS inspection tools to uncover the underlying styles? Perhaps the styles can change frequently, requiring them to be kept in sync in any documentation, when you could just use inspection tools to find the ".some-salesforce-class" in the CSS panel.

Where I’m coming from

I’m new to front-end development, so perhaps I am misunderstanding the philosophy of Browser UI development. If so, please help me understand better.

CSS styling can be frustrating for a minimalist who has a background in low-level programming in high-performance systems.

Request

There seems to be different expectations/philosophies involved in front-end development (e.g. ones that promote creative-expression). Please provide answers in a way that suggest these principles to help build my understanding of front-end development.

Any help, tips for a UI newbie, or insights would be appreciated, thank you.