Actually, with that last comment you've probably hit the nail on the head. You see, the BSA often leaves flexibility in thier policies so as to allow different local Councils an ability to adapt National guidelines to the community's own environment.
The amount of adaptation that a local Council is allowed depends on the type of policy. Membership policies tend to be the least flexible, but to me it seems that the deliberate addition of the word "avowed" in front of homosexual is, at the least, meant to establish that something other than merely being homosexual is necessary to ban someone from registering as a Scouter. It's more than just homosexual status that disqualifies you from the BSA, there's got to be some behavior too. The BSA, as it often does with other policies, allows local Councils some latitude in deterimining what that behavior is.