It would be provably false in some sort of alternate world where Steam was the only avenue to purchase PC games. With physical retail, Amazon, and eBay in the mix, buying this game at a price well below $60 was feasible long before now, and will remain that way even if Steam jacks their exorbitant rates back up. The Xbox marketplace can put a price of $19.99 on Sunset Overdrive all it wants, doesn’t change the fact that game has sold for under $5 brand new.
And your mention of Xcom touches on one of the main issues: few of the buyers for Civ will be buying it for the first time. So that means after the sale expires they would be asking people to shell out $60 to have a mobile version of a game they already purchased, presumably at or around $60 (since anyone hardcore enough to even consider rebuying the game likely purchased Civ on the PC near launch). And that’s the minimum. I haven’t played Civ 6 sadly, as I am primarily a console gamer. But if that DLC it has costs money, then it’s even more of an investment to then go and repeat.