Yes, it pretty much depends on what and how you're trying to compile. Incremental complication helps a lot, as does keeping sbt shell open and not restarting sbt each time.
Just reading the later variant makes me wonder "What are we (a)waiting for here? For set_debug to succeed?". I'd definitely stick to the former variant.
Perhaps, it's just not the best example and there are better usages than the one chosen to illustrate it.