I think that it has more to do with the initial shaping of the cutters. Round chain comes that way from the factory.It’s funny how with square filing the general consensus is that the grinder is better, but with round filing the opposite seems to be the normal view.
While you can buy some factory square ground chain, a lot of guys convert it from round, then square file to sharpen.
With the cost of some double bevel files being 12 times that of round chainsaw files (!!!!!!!!!!!!), it is expensive and time consuming to use a file to convert. But Silvey and Simington grinders are pricy, even used.
I am watching this thread with interest:
https://www.arboristsite.com/threads/i-can-square-grind-with-my-round-grinder.358884/
Philbert (and other stuff)