DX12 has.explicit multi gpu as an option for any developer, and this method does not suffer.from the same issues as SLI/Crossfire.
The problem is that multi GPU systems are getting redundant from a price to perf standpoint when all factors are considered.
So, as an example, if you could run 2 Vanilla RTX 2060 (non super cards) you would have the same number of cores/ROPs as a 2080 TI, but with less ram, 70% scaling, and priced at $700.
Granted $700 is cheaper than $1200 but when you examine Nvidia’s leaked share holder memo, they literally just priced everything up a tier.
IE $1200 2080 TI is what the $700 2080 would have been, and it could have sold for $700, with a decent ROI prior to the crypto boom.
IE same price whether single high end chip or dual low end chip, where the multi GPU option offers no guarantee of extra performance.
Nvidia have just gone insane on prices.
If you can afford $700 then you can get 1 single 2080 that will always work better in all games, without requiring more effort from Devs.