I think it's a power advantage, not performance.
The benefit is they can charge you $200 for memory they bought from Samsung for $15. There’s no performance advantage to the user.
I’d love to know where you’re picking up LPDDR4X-4266 RAM for $15?
Are you actually asking? The spot price for LPDDR4X 16G is only $9. I was actually being generous. No doubt the contract price is far lower.
It seems weird to artificially limit the max memory if there was no advantage in it.