Ron, I've said it before, and I'll say it again: I agree that CFI-SPs can't give instruction in non-LSAs, even if their pilot ticket is something higher than SP. I agree that that's the intent of the rules. I agree that the FAA would get quite unhappy at a CFI-SP giving instruction in a 150 even if he could legally fly the aircraft as PIC. I have absolutely no intention of doing so. I would have no intention of doing so even if I had a medical to go along with my PP-ASEL.
Where we disagree is that you see something in the rules that I do not. I'm trying to understand how the rules as they are written prohibit doing so. I just don't see it in the plain language of part 61, subpart K. That subpart is what applies to CFI-SPs, and the FAA did a good job of writing it in plain language rather than the legalese of the remainder of the rules. They just didn't include that little detail.