Your JD, from the pictures, clearly has a more aggressive tread pattern then turf tires, or R-4's. Not even close to being a fair comparison for traction.
Second, how were you towing with the Kubota? Was the backhoe on the
B26 or did you have the 3pt arms with some kind of a rear hitch? It makes a HUGE difference on my
L35, whether or not the hoe is on. Wet grass can cause my wheels to spin if I am trying to pull something with the rear receiver. Having only the FEL on causes a huge weight bias to the front axle and tires. No 18' trailer is going to make up for almost the 1K pounds of "tongue" weight, I am giving up with the hoe off.
If you had one of the bucket receivers that many people have modded their tractors with and "pulled" the trailer while backing up in 4wheel drive, you could drag your trailer anywhere you'd want to.
I realize that you were just stating a fact, but you did yourself no favors with the wording. Glad you love your JD, but it's brand and color had nothing to do with your miraculous feat.
Stay safe.