The greasable hub has been on machines as far back as the early 1680s. My 87" had/has it. Info about it was'nt in the OM and access to it was not available. (which is likely why it was'nt in the OM) Its greable for longevity of the spines and because to replace the belt, you'll need to slide the hub over on the splines. To make that possible, it would be best to have slines that are not siezed from washing and dirt. If the 23xx are in the same spot as the older machines, the access will be on top of the pto housing just to the outside of the belt line. On the older machines, I take a small prybar up top with me and use the engine rpm notches to move the hub around til the zerk shows in the hole. There is a cavity that holds a lot of grease behind the hub. Fill that cavity, and get the grease to just show on the spines. Dont over grease it or you'll get grease flinging onto the belt. I use a high grade moly grease for the splines. Try to find a grease with an "anti-sling" addative and put it in a seperate gun and label it. Standard #2 lithium will not hold up in the temperatures that those spines get to.
EDIT: I see you have a 21xx. If there is not a hole to access the hub zerk, you will have to drill one. It is not a tough job. Ask your dealer for the location. They will have a service bulletin with the dimensions. I oversized the hole on mine a slight amount as when I use a new tip on the grease gun, it is a bear to get the thing off the zerk without breaking it if you dont have enough room to wiggle the hose.
The better question about the wet clutch is why did they go "TO" that clutch setup in the first place? Funny stuff to watch the factory use the customer as guinea pigs. They went from the belt clutching system to the wet disk clutch, and back to the belt clutch system. Horsepower was likely the reasoning. To take that much HP as the newer machines were putting out, it would've taken a complete redesign of the housing and mounting system.
If your engine is turned way up, you should test your clutch system on a regular basis. The more power you have, the easier it is to fog the clutch. Keeping the engaugement pressures and flow in their correct tolerances will help insure a healthy clutch. Also need to keep the accumulator in proper pressure.