Thing is. Most people that use their tractors, either borrow, or remt equipment that hooks to their tractor's hyd system. At that point, your hyd oil is contaminated. So, unless you purchase every item you connect to your system. you will most likely 9at some point) contaminate your hyd oil . Or, you change your hyd oil each time you use others equipment.
Having sad that,
Anyone can deny any warranty claim for any reason. You would have to hire a lawyer and sue to have repairs made.
I once owned a new Dodge Ram 1500 (1995 mod.) 3 year, 36 mo. bumper to bumper warranty.
About 1.5 years the dash cracked. I returned to the dealer for replacement. The dealer denied the claim saying I must have had the dash out and cracked it, as they had never seen a dash crack on it's own.
I requested an appeal from a factory rep. Two days later, I met with the factory rep at the same dealership. I believe the person that denied my claim and the factory rep have their game plan together, as the factory rep told me the exact same thing.
How many have owned a dodge truck from 75-97 ? era that the dash didn't just crack on it's own ? Yeah, I know, almost (if not) every one of them.
So, any company can offer any warranty they want. Stand behind said warranty is a different story !