I agree it is strange, but I still think there is a good chance the starting problem is connected to the manifold heater and/or "Timer Relay"
I had problem with my tractor turning over when the temperature was in the teens. It would turn over but very slow. The tractor was delivered without the block heater I had requested. When the dealer came to get the tractor to install it, I told him how the tractor would barely turn over below 20 degrees. I should add that the heater light never came on when I turned the key on.
The tractor seems to start better now, although we haven't had any temperatures in the low teens since it was returned. The dealer said he "optimized the electrical grounding" (his words). After it was returned the heater light would come on when I turned the key. Prior to its return I never had a problen engaging the starter when I turned the key. After the return, I had the problem twice. Each times I would leave the key on while I checked to see that trans & pto where in neutral. By the time I finished checking, the tractor would turn over. Both times the trans & pto were in neutral, but maybe a safety switch was still engaged and the movement of the levers switched it off. If it happens again, I'm not going to touch the levers and leave the key on for a minute or two before try to engage the starter again.
It is strange that there is no mention of the manifold heater in the manuel, but it is there; at least on mine. It sure would be nice to have an explanation on how it works. My dealer doesn't know. He said he was going to contact the service representative for an explanation.
Bob