It has been VERY low key hasn't it?
Especially when you compare it to the return of Barry, or even the Rebirth one-shot.
My thought is that DC are hedging their bets here.
If the Barry in the Multiverse book bombs, or the Wally is the Flash fails - they will quickly re-establish the 'Barry One & Only Flash' status.
I hope the Flash book sells gangbusters, and I'll definitely be supporting both books.