Just to confirm my own (limited) experience with regs…
If a reg key is constructed so that, when “pushed” (opened, depressed, mashed - take your pick) all the way down it opens the key behind it (the key to sound the next sharper note on the reg), it seems like this would present a difficult instrument to play as you would have to be very careful about how far you open the keys.
On my Quinn C set the reg keys only sound the hole they are supposed to (even if the key is opened all the way). I guess I assumed that this was how regs were supposed to be constructed - but I haven’t handled enough full sets to speak with any certainty.
If the key opens more than one hole then you are in deep sheet. It would probably cause the reed to screem into another octave and be quite distracting to the listener.
If the reg keys are built in a way that allows some of them to activate others, a common remedy is to glue pieces of cork to the undersides of the offending keys so they are stopped by the wooden blocks before they can touch another key. My Seth Gallagher C full set needed cork on a couple of them.
As far as I"m concerned, this still presents a difficult instrument to play!
My Rogge regs keys are set so that, on the bass and tenor regs, the B keys “over reach” and can depress the C key above it. I figure this is designed to be so. It lets you slide to these notes. The sound is not unlike Leo Rowsome’s sliding of these notes a la “Staker Wallace”. This is not to imply that I can play like Leo…is that clear?