Interesting. wonder what the odd's are that Kubota backs the new manuals?
On the one hand, theres probably been thousands of the newer BX series tractors that don't require the hydro oil change that are now well past their 50 hr service interval that have followed the instructions to a "T"
Thats alot of "possible" HST failures that they would then have to deal with "should" it end up as being a mistake in the manual and damaging to the HST.
Then you have the many dealers that have also followed those instructions to a "T", could they also be liable to their customers?
I'm no lawyer and haven't stayed in a Holiday Inn in quite awhile so I'm just speculating, just like every else in this thread

so I'm very interested in their response to JohnThomas.
It would seem that if that was a mistake in the owners manual that they would have caught it MANY moons ago and contacted all their dealers and owners to provide an addendum.
I doubt they would want their reputation practically destroyed overnight, (see Toyota) should BX HST's started failing enmass. They weathered their experiment in plastic bodies and their 1st attempt at reengineering their HST motion pedal assembly's but I doubt they'd weather having to repair/replace THOUSANDS of damaged HST's under warranty....
But then again, who knows if they have some sort of fine print somewhere that'll cover their, ahemmm, rearends in such a case? Course their reputation would suffer.....
My guess is, and since it's a free guess it's worth about what I'm charging for it

Changing the HST hydraulic oil in a new BX at 50hrs is unnecessary.
While it's cheap insurance and really not a bad idea, it's not really necessary.
Kubota doesn't require it in some of it's larger more robust tractors and there hasn't been a rash of them failing, and they've been working VERY hard for years......
My
BX23 required the change at the 50 hr service and I did it because it was required. The oil looked fine to the naked eye and the strainer didn't have any visable shavings, but I dipped and cleaned it anyways because it was specified to do so.
I don't change the hydraulic oil when not required so this mean this same oil is spec'ed to go at least 300 hrs inbetween changes. With this in mind, the only reason I can see that Kubota required the change at the 50hr mark was to ensure that any break-in materials within the HST were fully removed and they must have felt that a simple filter change and strainer cleaning wasn't sufficient enough, back then.
So, has their manufacturing procedure on the HST's changed enough now to where there's less of a chance of break-in material occuring? Perhaps.
Course the argument can be made that they had the technology to reduce break-in material contamination many yrs ago since some of their larger tractors didn't require a fluid change at the 50hr mark and they're still going strong.
I'll stop my rambling now and await the answer.
But I'll close with this, when in doubt, follow the manual and BP Ficks cork plug invention

Carry on
Dave