kubota will pick up the tab on the fluids and filter, but the dealer that did the recall has to request it. Most of the time they don't because it takes time. The process sucked when I worked at the dealer, sometimes took days weeks, even months sometimes (although typically a week for 99% of the requests).
The recall itself doesn't specify using new fluid and new filters, and that's a loophole that some dealers will try to use to recover a small portion of a money-losing recall. I only did 2 of them and both were MX's, and both of them sucked. Lost money (commission pay) on them. You can't do them in flat rate without hurrying and you don't want to hurry one of these, lots of parts to remove and then reinstall, and lots of ways to mess up.
with air conditioning stuff the refrigerant MUST be recovered and weighed for the proper amount per federal laws. At that point it's just as easy to put it back in once the repair is made. Hydraulic fluid could be done that way too but most dealers don't have any clean buckets laying around to recover and reuse oil, and most owners aren't fond of the idea of putting used oil back in. Way too many chances of dirt, clippings, rocks, sand, poo, whatever... falling off of the tractor and into the bucket while it is draining.
I wouldn't have any problem with it but I'd also question it, just exactly like the original poster.