I meant that the bishop is stronger than the rook specifically in the opening stage, and not in terms of the cumulative starting value (which includes the opening + middlegame + endgame). If you need to gain an advantage specifically in the opening, the bishop will do more in this regard than the rook.
In other words:
Starting value = Opening value + Middlegame value + Endgame value (since opening value is present, the starting position plays a role).
Average exchange value = Middlegame value + Endgame value (since pieces are usually exchanged in the middlegame).
I meant that the bishop is stronger than the rook specifically in the opening stage, and not in terms of the cumulative starting value (which includes the opening + middlegame + endgame). If you need to gain an advantage specifically in the opening, the bishop will do more in this regard than the rook.
In other words:
Starting value = Opening value + Middlegame value + Endgame value (since opening value is present, the starting position plays a role).
Average exchange value = Middlegame value + Endgame value (since pieces are usually exchanged in the middlegame).