On a 2003 Mercedes C230 Kompressor Coupe, 1.8 liter with auto trans, what is the fill tube for (with the easy to remove plug with finger grip tab) that is next to the transmission fill tube? It seems they both go to the same place so why is it necessary to break off the red securing tab to pull the top off of the trans fill tube when it seems you can use the other one for the same purpose? What am I missing?

What is the other tube for? Is it to check the engine oil level?

Thanks