Did they?
All I remember was a statement that there would be 7nm GPUs for gaming—well, duh—but without confirming or denying whether Vega 20 was one of those 7nm gaming GPUs. This sort of hints at Navi being the only 7nm gaming architecture (along with its replacement, of course), but it's not quite the same thing as stating outright that Vega 20 would be restricted to the professional market.
Besides, we could see another semi-pro Frontier Edition card, this time based on Vega 20, that could perform quite well in games, albeit at a prohibitive price. Then again, the Vega FE was released at a lower price than the 2080 Ti, so where's the line between a gaming card and a (semi-)pro one these days?
If you want my opinion, back when AMD first made this statement, they probably didn't know whether Vega 20 would be offered as a gaming SKU, because the competitive situation at the time of its release wasn't known; there were probably a bunch of unknowns about the final product and its production (performance, yields, capacity, etc.), and I'd wager that some of these things still aren't known very precisely. So my guess is that AMD will release Vega 20 to the pro market, and then evaluate whether it also makes sense as a gaming card—it could go either way.