Thanks for posting that info from the ATF. I probably should have been a bit clearer about what I was referring to. You are correct the ATF rules are pretty straightforward.
However, the FFL requirement for private sales we were discussing isn't an ATF regulation - it is a Washington-specific regulation imposed by our (relatively) new and VERY ambiguous and confusing I-594 firearms bill.
That is what you have to be careful to avoid running afoul of here in Washington. It is FAR stricter and puts way more conditions on the sales of firearms than the ATF regs.