I have to say that I thought it was all a bit much ado about nothing until my 170a flight test for my instrument rating. I was changing xpndr codes (on standby ).
I glanced down to check the code before I switched the thing on and blow me if I didn't find the thing reading 7700 and an examiner waiting expectantly...
The chances must have been quite a lot to one, but I have been a convert to changing to standby when changing codes ever since
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they bought their tickets - they knew what they were getting into