Howdy
Either that guy did not know what he is talking about, or you misunderstood him.
Let's get this straight, the pawl (some manufacturers call it the Hand) is not going to wear down the frame. Maybe after 20 years of shooting a few hundred rounds through the revolver every day, there will be a little bit of wear to the slot where the pawl rides. Or a burr can rise up. But that would take a heck of a lot of shooting over a long time. More likely what he was talking about is the hand (sorry, that is what I am used to calling it) can cause some wear to the ratchet teeth at the rear of the cylinder.
So lets go into a little bit of history of the Ruger Single Action designs. When they first came out, the old Three Screw Ruger single action revolvers functioned much like a Colt. Anybody who had any sense knew to only load five rounds and leave an empty chamber under the hammer. If a live round was left under the hammer, and the hammer received a heavy blow, for instance if the gun fell to the ground and landed on the hammer, the revolver would probably fire. Even if the hammer had been left at the 'safety cock' position, the blow could be strong enough to shear the notch or the sear, and the gun could fire. Incidentally, this is the same reason you only load five rounds into a Colt and leave the hammer on an empty chamber.
Because of lawsuits, Ruger changed the design in the early 1970s, to include a Transfer Bar. The Transfer Bar design made it completely safe to load a Single Action Ruger with six rounds and there was no need to leave an empty chamber under the hammer. Ruger stopped producing the old Three Screws and only produced single action revolvers with Transfer Bars ever since. Ruger called these the New Model single action revolvers. When Ruger introduced the 'original model' Vaqueros, which were really nothing more than a Blackhawk with fixed sights and a rounded top strap, they of course included a Transfer Bar.
But there was always a slightly annoying feature with the Transfer Bar designs. To load a Colt or a Three Screw Ruger, one placed the hammer at half cock so the cylinder was free to rotate. With the hammer at half cock, the hand and the ratchet teeth would line up the empty chambers perfectly with the loading gate. The hand engaged the ratchet teeth on the cylinder and prevented the cylinder from rotating backwards, it would only rotate forward. So you simply indexed the cylinder one chamber at a time to load the revolver. All was right with the Universe.
But with the New Model single actions, there was no half cock position on the hammer. Opening the loading gate freed the cylinder to rotate. The hand prevented the cylinder from rotating backwards, but because the lockwork had been changed, the chambers did not line up perfectly every time you indexed the next chamber. You had to push the cylinder around a slight amount more for a chamber to line up with the loading gate. The annoying part was if you rotated the cylinder a tiny bit too far, the hand would fall into the next ratchet tooth, and you could not back up the cylinder to empty or load that chamber, you had to go all the way around again. A minor annoyance, but it could at times be frustrating.
So when Ruger introduced the New Vaquero (confusing terminology, huh?) they installed a small spring plunger into the frame. The purpose of the spring plunger was to engage the ratchet teeth so the chambers would line up perfectly with the loading gate. No more frustration with going a teeny bit too far. Everything was right with the Universe again.
In this photo, the spring plunger is the small 'button' protruding slightly from the frame next to the cylinder pin hole.
So. What is the Free Spin Pawl? If the spring plunger is removed from the frame of the New Vaquero, the cylinder will be free to spin forwards or backwards when the loading gate is open. The spring plunger can be removed with a hex key after the revolver has been disassembled.
Why bother? Frankly, if you load the gun up with six rounds, there is no need. But in Cowboy Action Shooting, we are required to only load five rounds, with the hammer down on an empty chamber, even if you are shooting a Ruger. Part of the rules. So if you can rotate the cylinder backwards after loading five, it makes it simple to rotate the cylinder backwards to get an empty chamber under the hammer. Also, some guys like to spin the cylinder after loading their five rounds, to make sure they do not have any high primers. Then to get the empty chamber under the hammer, rotating the cylinder backwards might make it slightly simpler.
I have been shooting CAS a long time, and I can't think of the last time I encountered somebody with a New Vaquero with the Free Spin Pawl. A solution to a non-problem in my not so humble opinion.
Getting back to the problem of wear to either the frame or the cylinder teeth, you will have to spend a lot of time spinning the cylinder at 1000 RPM or so before you see any significant wear.