Had a discussion with a fellow S&W fanatic.
Lets pretend I'm a bullseye shooter who only shoots S/A and some of the chambers are out of time (only happens with a finger on the cylinder and when slow cocking) can this actually impact accuracy of the gun?
Imho no.

First, you should NEVER drag the cylinder on a S&W when checking the timing. These are Combat revolvers and by design are NOT as tightly fitted as something like a Korth or Colt Python. BTW the reason for this looser degree of fitting is to insure they will function after being dropped in the bottom of a muddy trench.

As for you accuracy question if the revolver carries into lock with the hammer drawn back at a normal pace then a very slight failure to carry up when cocked in super slow motion won't have any effect on accuracy because the cylinder will ALWAYS be in full lock. Think about it, you are shooting in Timed Slow Fire, are you really going to spend a full minute or more to simply cock the revolver?

PS: until the internet came about none of us ever worried about testing timing while dragging the cylinder or doing it at a super slow motion rate. What we did was draw the hammer back at a rate slow enough that we could clearly HEAR the stop drop into the notch. Basically we were drawing the hammer back at a rate about 1/2 the normal rate and it was only done so we could clearly hear that snick. If the revolver passed that test it was considered just fine. Because in real world use the Inertia of the revolving cylinder would insure it was always carried into full lock. I will also note that at that time Gunsmiths who were caught "dragging" the cylinder were considered to be the equal of car mechanics who checked fan belts with a small open pocket knife hidden in their hand.

If the cylinder locks up and the charge holes line up with the barrel, probably won't effect accuracy in your case firing single action. If the charge holes are off and you get some bullet shaving, yes then accuracy will go all to heck.

Thanks guys for confirming my theory.
I learnt the dragging methode from my local gunsmith, a couple of well reputable gentlemen on youtube and, of course, a couple of S&W forums.
Since you are quite a legend here (and I do keep many of your articles/posts in my evernote collection for future references): how do YOU do the timing check?

Edit:
Just saw your full post, my smartphone didnt show the last bit at first lookthrough. Thanks for the timing check description!

Also, some guns may not time up if the extractor is a bit worn or loose fit in the cylinder when there is no ammo in the gun. If timing is slow, put 3 or more fired cases in the cylinder and check again.

If the cylinder is lined up and the cylinder stop is in it's notch when the hammer drops than everything should be good. If the cylinder hasn't fully rotated when the hammer drops accuracy is going to suffer.