I have Tyler T-grips on a number of Smiths, some, like the 2" 34 in the picture below, for many years...and I have experienced no damage to the finish of any of these revolvers.
At most, you may find a little compression of the wood where the mounting fingers pass beneath the grip panels. Keep in mind there are different sizes for different grip frames and it is important to use the correct one. If you're real concerned, a small piece of tape behind the Tyler may give you extra piece of mind. Like anything, make sure they are installed correctly and remove them, along with the grips, when cleaning to check for underlying oxidation.
That said...I have seen some revolvers with damage or finish wear to the front of the grip frame that appears to have been caused by a grip adapter, but because none were with the gun, it's impossible to say what brand or size was used, or if they were attached properly.