If nodal enlargement is because of HIV, all the nodes around the body should have the same chance to enlarge. However, most of the nodes appear around the throat and neck. I think it is because all HIV+ guys have some infection in their mouth and lung, some times penis, some times stomach, some times skin. These infection never go away, therefore, nodes never disappear. OR maybe HIV itself can only slightly enlarge nodes, HIV plus other infection generate big nodes..
You didn't realize actually ask a question. Most of your comments are correct. HIV infection typically causes generalize lymph node enlargement. It is not unusal for some of the lymph node groups to be particularly enlarged. The three areas of the body which are particulary prone to develop enlarged nodes are the following:
head and neck because mouth/tooth infections are common
armpit since the hand is constantly being exposed to infectious agents
groin since the leg is constantly being exposed to infectious agents.