I am the one responsible for deciding what gets included in each release of Multi-Edit and I try to think about how each change effects users. The original design of the Search dialog was to allow the down arrow to bring up previous search data and the up arrow to bring up the word under the cursor with the last search data being in the Search field when the dialog is shown. The behaviour you got used to using was actually caused by a bug in the code introduced when other features were added. I felt that it made sense to fix the bug so the original designed behaviour would be available again. The reason I know the way it is suppose to work is because I designed the original code many years ago.
I also use the keyboard more than the mouse when using Multi-Edit so I know exactly what you are talking about but I still believe this was worth fixing as the behaviour is now consistent.