Why is there two drain plugs on a V6 (Camry) Transmission?

I was changing brakes on my 97 ES300 and I noticed a drain plug in the transmission that I never used before. It reminds me of the differential drain plug you have on 4 cyl Camrys. It's located on the driver's side on the rear side of the transmission towards the firewall. You can access it and see it if you raise up the driver's side front of the car. It screws into the side of the transmission not the bottom. Same round plug that you need a 10mm hex socket. There's a screw above it that looks like an inspection hole. I always thought the V6 Automatics have the transmission & differential in one fill. I use the transmission pan drain plug for changing transmission fluid, not this one.