There are a lot of variables.
I typically thin Minwax gloss polyurethane - because I feel I get better penetration when it is thinned.
IMO there it is too viscous out of the can to penetrate deeply. I have cut pieces where I applied thinned and normal polyurethane and looked at them with a dissecting microscope. There is deeper penetration with the thinned gloss polyurethane.
But every finish is different. Not all of them have the same viscosity. Not all the finishes (or wood) are at the same temperature.