It depends on the number of units sold in the EGS store, primarily, yes. (Steam profit share isn't contingent on units sold.) But if you actually read the post I'm responding to, that is the post that says that it would "always" be better for developers for people to buy their games on Steam—I'm the one saying that it depends.
But it also depends on the actual number of guarantees left.
If your game has only sold like 50% of the guarantees in one year and the sales were frontloaded because of interest and discoverability, it is quite possible that the company would prefer that all new purchases are on another storefront where they get money immediately and not 2 or 3 years down the line. And Supergiant is currently advertising the heck out of Hades to be wishlisted at Steam.
And even if there are only like 1 or 2 months left until Supergiant gets the sweet 88/12 cut, it is still better to market the Steam release. it means discoverability in Steam if your game sells good and is wishlisted by many people.
The insane thing is, It could also mean that Epic has no interest in the game meeting its guaranteed sales goal. The exclusivity is over, the game didn't really do well (we are speculating that the guarantees were not met, a hypothetical situation for argument's sake) and the guarantee is a sunk cost for Epic. So why bet on it further. they have other games in their pipeline who are the hot new stuff and who hopefully bring new customers to the store. So Epic will concentrate on the new titles.