> how is running in debug compiled mode different than just...running the code normally?

It's not. By default, the debugger will recursively interpret any nested function calls until it encounters any intrinsics, since breakpoints can be set inside any functions. Compiled mode means the debugger won't do that for functions in a certain module (e.g. Base) and instead invoke the function like you normally would, so breakpoints either inside those functions or -- if functions from other modules are called from inside the compiled functions -- also breakpoints inside those will be ignored.

The problem is that when you compile code you can have things like constant propagation make it so that your breakpoint just isn't in the compiled code. Finding the right balance to make it look like your code is running the way you expect is really hard.