The keys for the rtv, bx tractor and the ZD series zero turns are the same and double sided.
The L series tractor uses a single sided key. Look at Messicks for a pic and see if it matches.
I bet you’re right, they changed the switch because of the key availability.
If so you can buy a new switch or take your key to a locksmith. I had to put a new switch on my zero turn couple of years ago. I can’t remember how much though. Seems like it was $30 or $40?
I don’t know offhand where my Kubota key ring is. I’ll try to find it and post pictures.
Just thought, look on ebay. They have all kinds of Kubota keys listed with pictures
Jim