Writing code is different than reading code, it suits different work patterns. One is dealing with software architecture and the other is doing software archaeology.
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.
This is maybe one of the greatest advantages I have gained in my years of experience at one company. When I started, I was inheriting the code of other people, with all the baggage of trying to understand it and keep the mental model intact when I needed to make changes. Over time, I've largely rewritten all of the products that are still current, as requirements and dependencies have changed. I'm reminded of the probably apocryphal story of Nikola Tesla and Henry Ford[1]
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.