In my opinion, the deck wash ports are useless. First you are using water in an area (the deck) that is very difficult to dry properly and help prevent rust. Second is that you are using water which is much different than grass being flung about by the blades.
Where I live in northern Florida, the deck wash ports are completely unnecessary. The soil around here has a high sand content which actually sandblasts the interior of the deck on every mow. I also do not mow wet grass.
My new ZT2 60" has no deck wash port. I think Cub Cadet quit installing them. My JD 48" has a wash port but I wouldn't use it for any reason. All they do is soak the stuck junk and when you put it away, the acids attack the underside of the deck. That is just a silly bit of useless junk that falls into the same category as screen doors on submarines.
I bought my ZT2 in late May 2021 from Home Depot as the local Cub dealers had no stock. It is a 2021 model. Figured this out from investigating the minor transmission changes begun in the 2021 models. The Cub parts guy told me they changed the trans configuration with the 2021 model. They did away with the plastic external transmission fluid expansion tanks in favor of internal expansion chambers and a vent plug. Same ZT2800 transmissions otherwise.
I don't know when they stopped the wash out port or if it is no longer standard on the 60" deck.. There is a place for it in mine with a plug in it. I have the 60" deck, not sure if that makes any difference. I'd remove it if it had the wash out port installed. Just my opinion..
Just a note: I ruined a blade on a hidden pipe in tall grass. I had been mowing very tall 8 to 10 inch, very wet grass for about 3 hours. While replacing the blade, the underside of the deck was remarkably clean, despite the wet clumpy discharge I had been seeing. It was free from the usual built up clumps of wet grass. Luck? Good deck design" Who knows? You might have a look under yours to see if there is anything clumped up under there.
I'll do my normal year end 100% scrape down and power wash followed by fresh primer and paint.