The BIG difference however is that a B-2 entrant MUST establish that they have and maintain residential ties outside US. As you point out, there is no such requirement for TN or TD. So there is actually a greater risk of denied entry based on immigrant intent for an entrant on TN, for that very reason.
I agree that the risk may be low of CBP putting the facts together, but it is there, and of found, the denial is not based on mood. The denial wouldn't be due to a "bad mood:, it would be due to intent.
Why else would CBP/USCIS have had to issue specific guidance to their staff not to deny TN/TD to I-140 applicants?