In the described catfish role, you don't get to spend any meaningful amount of time thinking about how to best implement the next thing; sure, you do some of that, but almost all the time gets spent trying to understand how the heck that thing was implemented (and why) (and why??????), and that means that (a) you don't really get progress unless you're looking at or touching that artifact, and (b) you really want to avoid context switching; if you've spent three hours building up a vague picture in your mind about what something large and weird is supposed to mean, then you'll have to repeat half of that if you take a lunch break and talk about other matters. When you do figure that out, though, the fix or rewrite generally is quick, easy and routine.