The Bloomberg Terminal uses several different UI methodologies depending on use case -- many functions (applications) are absolutely TUIs whereas Launchpad is more mouse-driven.

> In both cases, people operating these systems develop muscle memory for their everyday usage.

I worked as a UX designer at Bloomberg and when we had to modify existing functions we were careful to maintain shortcuts and keyboard navigation. In a couple cases we even ended up re-implementing UI bugs that one or more users had grown accustomed to. I've never worked anywhere quite so committed to backward UI compatibility, but that came at the expense of a steep learning curve.

I had to reverse engineer the 1980s style ASW screen and replicate it, bugs and all. It had on-screen side effects where hitting TAB would cause numbers to recalculate according to a buggy LIBOR interpolation rule that persisted until ASW got replaced around 2010. Yet traders would take ASW as gospel.

I spent many evenings hand-marking dozens of Bloomberg screen prints to satisfy Accounting that my calculations were right and our Bloomberg operators were getting fooled.

I never worked on ASW or its replacements, but assuming they fixed the calculations in one of the newer swap curve functions I also wouldn't be surprised if some poor developer had to add a "compatibility mode" with the old calculation to avoid breaking someone's longitudinal analysis or satisfy some important user who prefers a stable calculation to a correct one.