I don't know when this changed, but the opacity of the d-pad control option doesn't go down anymore when it's set, and instead stays at 100% opacity. The joystick option has the opacity work as intended (except with the buttons, which may be included in this bug).
Screenshots attached include two new screenshots showing current behavior, and an older screenshot showing older behavior. All screenshots were taken with HUD opacity in video settings set to 50%. Newer screenshots have no resource packs enabled.
Please close this issue as I had not realized this was added to the (still poorly implemented and experimental) customize controls section, which has it's own set of issues (like the default not being savable, as seen in MCPE-174886). I still can't change the opacity without the d-pad being far too high up compared to how it should be, but that isn't related to this bug.
I was also able to temporarily fix by editing options.txt under gfx_touchDpadOpacity and gfx_classicButton2Opacity, but then the size is too small... Again, unrelated to this issue. I can at least see my maps in offhand again at the detriment of my carpal tunnel.