Yup, the Exage 500 CX and Deore LX rear derailleurs were nearly identical. I have both, no significant differences. Cosmetically different faceplates. Even the model numbers were nearly the same.
The Exage 500 CX group on my early 1990s Univega Via Carisma included "integrated" brake levers and indexed thumb shifters. Both the front and rear derailleurs were indexed, no friction mode available. The thumb shifters were modules that bolted onto a mounting plate that extended from the brake lever housing. The setup located the shifters under the handlebar, which felt more natural to me.
It was a great setup while it worked. Not sure why it didn't catch on, and appeared to have been fitted to only a few bikes for one or two years. Photos of this group are scarce. I need to photograph my own and upload 'em.
The brakes can be used without the shifters -- fortunately, because both shifters finally quit a few years ago. Flushing with WD-40, etc., didn't help. The shifters can't be used without the brake set, unless the owner fabricated a handlebar clamp from scratch, which probably wouldn't be difficult for a metal shop, or perhaps a 3D printer.
Currently I'm using the brakes, despite the gawky looking empty mounting plate, sans shifting modules, because they work well. I switched from flat (well, slightly arced) handlebar to albatross swept bars and bar-end shifters a couple of years ago. Great setup for converting a MTB-lite/gravel-ish bike to an all around city/path bike.