Yes, the wiring is as you describe.
The main issue is that the resistance is twice what it should be, and ultimately the power is less by 5 to 10%.
I have traced the patterns on the board, they are in a zig zag pattern going down the board like a ladder.
When A-B and C-D are connected, every trace is heating, like 1111
When B-C are connected, every other trace is heating, like 1010
When A-B are connected (C-D open), every other trace is heating in groups of two like 1100.
The whole point of 24V is to make heating faster, and A-B only is the only way that can be done here.