Has my seeing alien spirit involvement almost universally using the Lightworker Healing Protocol been due to sensing their placement of a portal within the client?

Indeed this is the case and explains the facility they seem to have in having such a powerful ability to be influencing individuals, but yet come and go. This does create the implied question as to how they manage this so effectively, and the answer is, as you have intuited, once they gain access, they create and leave behind a portal for subsequent incursions. This greatly simplifies things and saves considerable time and effort to keep people under close watch, waiting and waiting for an opening provided when they may drop their guard for a time, through an emotional upset or physical impairment. With portals in place in almost everyone, they can simply make the rounds quite quickly, and seeing someone uninfested with spirit meddlers, can quickly summon meddlers without a host and shepherd them to the portal in question to move right in, and this becomes quite efficient in their direction of the infestation.