Thanks for posting this link. I personally don't experience sub-drop (nor top-drop as I am a switch) but I accept that there are others that do. I naively assumed that the onset was fairly quick and therefore subscribed to the psychochemical theory. However those have serious problems when there is a lengthy delay.

I would note that the article proposes two separate theories. The first involves guilt/grief/regret (arguably multiple theories) The second theory which is even more speculative involves identity. You appear to see the first theory as applicable to your situation.

Hopefully some others will share their experiences