Some of that is incorrect according to the Fed rules.
26,000 GVWR and below with air brakes does not require a CDL. An air braked truck rated at 26,000 GVWR or less can tow a trailer 10,000 GVWR or less for a gross combined weight rating of 36,000 legally without a CDL.
Now a juice braked 1 ton at 13,000 GVWR pulling an 18,000 GVWR goose neck would require a Class A CDL according to the Feds.
As far as transporting diesel one can transport more than 100 gallons in a single tank. Thunder Creek has figured a way around the rules to transport a lot diesel legally without a CDL and hazmat.
https://thundercreek.com/products/multi-tank-trailers.html
Clear as mud because it's government.
I've never known for sure, I posed the question to two different VT AOT officers, got two different answers.
I once owned a Chevrolet C65 with air. It was titled at 25999 LB but nameplate GVWR was 27500. I got two different answers as to a need for CDL.
When I added a 9 ton trailer, there was no longer a doubt I needed CDL.
VT DMV threw every obstacle in my path they could. I showed up a total of six times for my tests. Four of these trips were in a borrowed (bartered) truck & trailer with licensed CDL driver accompanying me.
A written test for Learner's Permit.
A written test for License. At the time of this test I was aware VT would later that year require a medical card for all CDL licenses, but none was required for in state use. I specifically asked, was told none would be required.
I arrived with truck, trailer, & accompanying CDL driver, only to be refused for lack of a medical card.
"You told me I didn't need one."
"Who told you that?"
"You."
"Well, the law changes this year, we are enforcing it early."
My doctor was pissed! I didn't realize I was kicking over a hornet's nest. He said: "I'm qualified to teach other doctors, & nurses to administer the test, but I myself have to attend a weeklong course to keep my certification."
Next appointment he failed me on the Pre Trip Inspection. I failed to inspect trailer headboard & landing gear. I pointed
the trailer wasn't equipped with either. "You need to mention that."
I also didn't inspect the windshield & mirrors. I hadn't adjusted the mirrors. I responded: "I did that before driving to Rutland."
Next appointment was made over the phone. When I arrived he informed me he had no record of me having an appointment.
Last appointment, my Licensed driver, borrowed truck & trailer backed out a few days before. I scrambled, spent a couple thousand on my own truck & found a retired trucker to accompany me. I took two hours on pre trip inspection, crawled around under the truck way too long. I pointed out lack of landing gear & headboard, but checked function of jack. I checked the windshield & mirror adjustment. Asked him to adjust passenger side (it was already perfect). He finally cut me short on pre trip inspection.
I finally got to take the road test & docking maneuver.