No, it's not irrelevant. If you're trying to figure out what gets passed up the call stack, you need to trace it through. Being able to plug in your own values into a single method call via the REPL isn't helpful if you're trying to analyze what really happens when it runs. Either you need to run it under a debugger, or manually trace it through. In a static language you just have to read the type signatures.
As mentioned by JackC, if you need to understand the context in which a method is called, use a REPL. But to understand what a pure method does should be context free, by definition.
