Concurs with my observations. However, at short range for portraits, I would seldom use the full aperture, too much of the face being too obviously blurred, so there is no "problem" for me using the 105/2.5. f/5.6 is often my chosen setting for headshots, no matter the FL, at least if the background is not overly disturbing.
I also reported here, earlier, that (for instance) the old Tamron 90/2.5 was definitely the better lens at 1.0-1.5m distances in terms of sharpness wide open, and LoCA. However the Nikkor definitely has the best background blur under such circumstance. No wonder the Tamron does its job as a (primarily) macro lens...