rename, rename.ul (perl one) and mv are essentially different tools of the util-linux package (one of them isn't part of it), that though can do similar tasks (
mv can rename files, the same as
rename), they are highly specialized tools.
I imagine rename was meant to refer to the action of renaming, not the actual tool, but there's no tag wiki to be sure. I don't know where you came up with 169, but the synonym only took effect 40 times, so the rest of the time people have been choosing rename to describe their problem. I dropped the synonym for now in case there's actually a need to distinguish usages of
mv from just generic "renaming files"