Flamestrike
Legend
I think it might be more that they are reprinting because players are less likely to buy a book for a setting but more likely to buy one which has options. If you don't care about everyone but want to play an artificer this let's a player buy something which is better than a setting book as it contains a bunch more player options that they might also use.
I had it confirmed somewhere it was PHB+1. It was the same reason they reprinted the melee cantrips in Xanathars.
If they didnt reprint the Artificer in this book, Artificers at AL tables would be stuck with the PHB and Eberron Explorers guide as their +1 (denying those guys the new feats and archetypes and race options from this book).
Really, they're just kicking the can down the road though. Unless they release a revised PHB with the Artificer in it, they're kind of stuck having to do this every time they release another +1.
Im pretty sure they know this though, so I wouldnt be surprised if we dont see a revised 5E CRB's hit the shelves next year some time.
Not 5.5E but more a compilation of what's come before, with the Artificer a core class with the rest of them.