While if you reduce your bet size exactly as you suggested, the above statemwents are absolutely true, in terms of what your asking. however, there is another angle of attack for playing multiple hands
With a fixed amount of cards to be dealt, its in your interest to play multple hands to increase gain/time For simplification of concept ***Im going to use 2 cards per round as an example.***
If you play head up, you and the dealer consume 2 cards, for a total of 4 cards/round. Ultimately you consume 4 cards per Hand dealt to you
If you play three spots, you would be consuming 8 cards per round. But since you are receiving three hands, you only consume 2.66 cards per hand dealt to you.
You will play and receive more hands before the shuffle if you play multiple hands. If they are at a player advantage this is a good thing since monster counts are less common. Playing in this manor should improve your win rate vs time, but depending on how you bet not neccessary your win percentage per dollar as your asking about.