Ok, yes, in at the beginning won't harm your meat. I don't use the Anova app, so i can't confirm the starting time control.
Of course the frozen meat will add to the preheat time. It's like adding a block of ice. Don't overlook frozen meat also adds to the total cook time and i don't know if the app's control can be adjusted for frozen meat.
As an example, a 1 1/2-inch thick frozen piece of meat requires 3 hours to reach temperature equilibrium with the water bath.
The same piece of completely thawed meat requires 2 hours to reach temperature equilibrium.
Many cooks do not realize it takes many times the amount of energy required to thaw meat than to raise its temperature by 1 degree once thawed.