I had to look at the target trigger on my Model 17. It appears to be the same as yours. That being said, I never experienced an accidental discharge when holstering my revolver. I suppose what the "old-timer" said might be possible, but I don't believe it probable. The area of the holster that covers the trigger/trigger guard area would need to be exceptionally tight to cause the trigger to move completely through its rearward arc when holstering the firearm.

If it were me, I would (with an empty firearm) try to duplicate the aforementioned action and determine if this is in fact a valid concern. As an aside, some older holsters have an "open" trigger guard area making this discussion a moot point. Granted, from a security standpoint an open trigger/trigger guard is not optimal. But remember, there ain't no such thing as a free lunch.

Some people more knowledgeable will be along shortly to provide more info.

Jm2c

JPJ