Well, I hate to mention it but there are times when it seems like the folks who should know the most, simply do not! This may be one of those times----or I could be totally wrong and looking the wrong place!
But Winnebago does do a great job on your Rv at putting great info online for finding how things are put together and plumbing is one where that counts a lot, so do a look here when needing to know things like where the plumbing or other parts are located.
There are several different options which I did not know about for your RV but all seem to show near the same for the flushing as a stand alone connection in a different compartment, not the normal connection!
This is where to get some good info but it takes a bit of guessing/learning curve to get to what you want:
https://catalog3d.winnebagoind.com/menu/Parts.htm
Plumbing here:
https://www.winnebago.com/Files/File...m/Plumbing.htm
Electrical here:
https://www.winnebago.com/Files/File...ram/Wiring.htm
But taking a look at the first one and guessing a bit on exactly which RV you have, I found the following pictures to take a snip and see if it matches your RV! left snip is the front view and if we turn it around to get a view of where that tubing leads, it winds up as in the second snip and going to an item labeled flushing.
Click this snip to get a better view?
But do you have a compartment a bit further forward with a different hose fitting for the flushing system? That looks true from my guessing but if not let me know which exact model and build, early or late in the year and we can take a different look.