Simplicity Conquest "transmission" light

I have a 23/54 Simplicity Conquest which I believe was sold new in 2008, making it now 6 years old. I purchased it in 2009 with 30 hours on it. I have since replaced the engine, the PTO, and one arbor, I do a lot of mowing and I am certain it has over 600 hours on the transmission. This summer the transmission light on the dash began flickering, which did not surprise me. However having been through failing hydros before, they generally lose the ability to climb grades and then just fail. This was/is still running strong, just the light flickering. I changed the fluid and it still runs strong, actually my handy dandy retired neighbor changed the fluid and told me that the light is actually an engine oil level light. The manual says it is for the transmission and says take it to a dealer when that light comes on as the transmission is not owner serviceable. The image on the dash over the light is one of a transmission. There is however no wiring connected to the transmission which I can find, so I wonder what causes the light to go on and off. The wiring diagram, not really a schematic, in the illustrated parts breakdown indicates the thing is to be connected to an oil sensor. It has been 2 years since I replaced the engine and I do not recall an oil sensor on it.



So does anyone actually know what that light connects to? Also my engine does not smoke nor leak which I can observe, yet it needs frequent oil. Has good compression 23HPB&S vanguard now 2 years old.

What is the most likely cause of the oil use?