pichu17. Weight on Wheels is in the Main Landing Gear. Ground sensing is in the Nose Gear. The Take Off Configuration Warning depends on the ground sensing – of the Nose Gear.
Why is the critical TOCW fed from a single point option – the one with the highest chance of failure?
The only reason I can think of is that this arrangement allows disabling of the TOCW audios (ground checks etc.) with the least affect on other systems. I’ll bet there’s an interesting design history on this; and I suspect the first DC9/MD80 TOCW was originally wired to the WOW switch.