Yes, heat transfer is what you will end up with (there will be no circulation).
Yet, with two holes, maybe you will get twice as much.
No joking: I liked/used the two hole plates because
I like the symmetry of the appearance of the two tubes on that side of the engine. A better appearance over no better function?
I still use the two tubes on the plate under the original intake and a Holley AA-1 two barrel carburetor. It heats up nicely and runs very smoothly. I'd bet that a one tube set up would be just effective.
