Yes, it is a transfer bar system as you describe.
All I can think of is overtravel of the firing pin and extra wear on the firing pin, firing pin spring and or firing pin channel. Maybe the firing pin is tapered and the overtravel, because of not hitting a primer, can make some kind of contact with the firing pin channel causing extra wear.
I bought my made in January 1992 Stainless 6 inch 689 in 1992 and have done a fair amount of dry firing without snap caps and have had no problems. I would advise to buy snap caps if I were to train and use the 689 in dry firing scenarios. Mine gets very little use. I get it out every few months and wipe her down and invariably snap a couple off, but total dry fire count probably is less than two or three hundred at most in 27 years or so.
It has a sweet double action and almost hair trigger single action right out of the factory that has never been touched. Feels as good as many Smith & Wesson's that have had work on them and feels better than most of any brand being produced today. Definitely finger off the trigger in single action mode until aimed down range and ready to fire. I have touched it off a couple times before wanting to while almost ready to fire. Funnily they were some of my best shots of the day!