I currently work at a small development shop whose main product is a debugger. The process you describe is our standard way of navigating the code base - load the debugger up in the debugger and poke around.

I'm not a fan of this workflow. I like to start learning about something from the top down and there is basically no way to do that with this method. It's great for getting into the nitty gritty details of the code to solve a problem, but it's terrible for learning how the different chunks of code fit together or how the code looks from the top. For our developers with many years of experience, this isn't a problem. For newcomers like me, it is.

It probably doesn't help that this particular debugger is both written in and used for assembly language. If it was in a higher level language, I could probably get more of a top level view from the commentary, meaningful variable names longer than 8 characters, and the fact that 10 lines of python does a lot more than 10 lines of C which does a lot more than 10 lines of assembly.