If the factory grease were so good, we would use it to lube the chain after the factory coating wore off. Right?
The comments of use the factory grease until it wears off are in the context of most people using drip lubes. They aren’t talking about doing that when waxing.
When you use drip lube, the chain wears out much faster than with wax. As explained by FF, most good chains have a surface treatment for better hardness and lower friction. Key word there is surface. Once you wear away that surface, you get higher friction and significantly faster wear. A big advantage of waxing is greatly improved time before you wear away that surface layer, thus longer chain life.
But even when using drip lube, I absolutely hate the factory grease and strip it immediately.