I'll give my case of what happened to me.
I was playing MGSV when it launched. I was playing single player. At some point the game updated. Between the game updating, and me playing, my internet had gone down. I launched MGSV and it wouldn't run because it said it needed to authenticate, and I had no internet to do so.
This gives an idea of one instance where authentication is required, and not completed automatically and preventing playing the game. My guess is that there is likely a periodic check as well.
Doing some testing now, I just went into Offline mode and tried to launch the two Denuvo games I have installed, MGSV and DOOM.
The last time I played MGSV was June 22nd, and the game launched fine offline.
The last time I played DOOM was June 26th
But it had an update on July 1st, and trying to launch it offline gave me this.
I don't know if there is a recheck it does, but regardless it seems like there is definitely an online check necessary after install and/or update.