I didn't say atat, what I said was....
Chevron All weather THC synthetic and Shell Rotella hydraulic fluid are both Kubota Approved' IOW, meet or exceed Kubota specifications. Not endorsed, meets requirements. Kubota is going to want you to purchase their lubricants. I don't, never have. I do use Kubota filters however. One thing that always irked me about Kubota hydraulic fluid is, it's clear so it is very hard to ascertain the fluid level on a dipstick equipped tractor (both mine are). Chevron THC is dyed orange (of all colors) so it's easy to see on a dipstick.
I believe with over 3500 hours on one tractor and 2000 hours on the other, if I was going to have a lubricant related issue, I'd have had it long ago,
I do a Blackstone oil analysis every second oil change and every fluid change and Blackstone tells me everything is hunky-dory.
I put more hours on tractors than probably 95% of posters on here and my hours are hard agricultural hours, not mowing ;lawns or playing wannabe farmer. I work them and I work them hard for long days at a time.