May I suggest you select standby first.
Then there is no chance of transmitting an unwanted code as you cycle through the box to the one you wanted to send.
Just like everything else related to flying safely - Unless you KNOW BETTER FOR A FACT, why rely on old-wives tales, mythology, bull!!!!, tradition or the belief that the kit will not let you down when you don't have to?
Be careful, be safe and do the sensible things.
Its just a thought I've been using for 30 ys of flying.
P.S. If you turn C off cos you might get noticed in CAS - you should be. The accompanying transponder code may just help to ensure the correct license gets pulled.