I think that by "the boat rotates where the front edge of the keel hits the trailer as you drive out" Brian means this, which is about what I observe:
Because (when you first start) the trailer is at an angle and the boat is level, when the bow is as far forward as it will go (limited in my case by how far in you can winch the strap on the eye, without breaking it off) the keel is not directly above where it should end up. As you pull the trailer out, the front lower "corner" of the keel rests against the wood/carpet keel tray, and the boat is still not at the same angle as the trailer, so the rear of the keel is not yet sitting on the tray. As you proceed pulling to get it "unfloating", the boat tilts back to the same angle as the trailer, with its pivot point being the front corner of the keel. That tilting action pulls back on the winch strap and eye, and if they were pulled in too tightly to start, the leverage can damage the eye. To avoid this stress, I don't pull in quite all the way on the winch strap, leaving just a bit of slack - I'd guess about 2, maybe 3 inches less than fully tightened. That means the boat ends up a bit further back than ideal.
Since it only has to move about a couple of hundred yards and at a slow speed, I have never needed to try to drag it forward to solidly attach to the trailer.