Something's not right. In post #59 you said top right you had orange wires and bottom left you had red wires. In post #62 you show top right as battery terminal and bottom left as solenoid terminal. In the schematic red wires should go to battery terminal and orange wires should be connected to the solenoid terminal. Do you see the difference I am seeing? As I see it the engine will only turn over with the deck down and foot off the brake petal.
Ok, I think what you are seeing is the difference between the two switches - the original switch & the new switch (which I have not used). What I said is correct, the original switch has B (red wire from battery) at bottom left and S (org wire from solenoid) at top right. The NEW switch has the B and S in reverse positions (as well as the L & X).
Stated another way, if you look at the factory schematic, the original switch in my mower matches the schematic exactly - red wire goes to bottom left & org wire goes to top right. (white wire goes to top left & vio wire goes to bottom right).
I had thought the same thing you did - that the schematic made it look like the mower would only start with deck down. What I know for sure is that the original switch is wired as I stated above and before it broke the mower only started with the deck UP.
**As to the difference between the two switches, the only thing I can think of is that the switch for the B and S is a simple single throw type and only requires an ON/OFF connection, meaning that it apparently doesn't matter whether B or S is top right or bottom left so long as they are limited to those two positions. Either that or the NEW switch simply isn't compatible with my mower. That's why I never tried putting the new switch in. But since the original switch was tested out of circuit and tests good it shouldn't be an issue.