You're both probably correct in the points you make, but the thing is throwing all this information around haphazardly is what helps cause all the confusion like sam5570 says. One guy says something about CDL then others start chiming in about DOT numbers. Then they start piling on about medical cards, logs, insuance, inspections, fuel tax, weigh stations, etc. and what one state regulates vs another. CDL and DOT registration really have nothing to do with one another other than they both relate to commercial vehicles.
DOT regs start at 10K weight, CDL generally starts at 26K. CDL is for all driving, DOT is only for insterstate commerce except in those states that require it for intraste as well. There are a lot of trucks that have DOT numbers but you don't need a CDL to drive them. The opposite is rarely true unless you are operating within one of the states that doesn't require DOT numbers. All I'm saying is that it's confusing, can vary by state, and you can't just lump all the regs together.
I'd like to see it clearly spelled out somewhere about what are the requirements and regs you have to meet when driving a vehicle needing a CDL versus what you have to do when you're just in your diesel pickup with DOT number on it.