My feeling is that this came from the first generation of Westerners coming into Gyan and going, " Oh, Dadi ... look at this! You look like and angel, you are an angel! " and then it was adopted. I asked in the BK forum when the iconography of angels entered the BK lore. If anyone else knows, I'd appreciate an answer.
I wanted to copy and paste a non-BKs theory about angels by way of a polemic. In truth, although I do not know, as a working theory it is not to far away from my own. You will see immediately the parallels to BKWSU in both the " incarnation of Shiva " story and the " Honeymoon Period " phenomenon.
Angelic entities seem to follow the same pattern in dealing with people. Known by different names; "Watchers" "Guardians" "Gatekeepers" their true nature is to keep humanity from progressing in any way ESPECIALLY in the area of mind power or knowledge of the 4th dimension/astral. They are like guards in a concentration camp. The "Watchtowers." To keep humanity in chains, enslaved and without power.
Those who are without and delve into the occult a little too deeply will often meet with unpleasant experiences (again, FEAR is used as a means of control). One way or another, those who are without are often deceived into relationships with angels. Of course there are variations, but here is what to look for - you will see this if you read anything about people's experiences:
The angelic entity intrudes. Most often the creature is uninvited and takes it upon itself to barge in on someone's psyche totally uninvited.
The entity uses love to lower the victim's defenses. This is done deliberately and masks the entity's true intentions. The victim (human beings are emotionally vulnerable - how many serious mistakes have been made at the mercy of our emotions) feels the "love" and is deceived into believing this is a positive visitor.
The entity never explains much or gives the victim any valuable knowledge. Most questions are not answered, if they are, they are in riddles or nonsense. Any information given is either incorrect or incomplete.
Often, the entity will make a statement that it is coming to warn the victim and/or humanity of "erring ways." This many times has to do with anything the entity deems as a threat to their total control, in most cases playing upon the ability for one to defend one's self; humanity's use of mind power for psychic self defense is EXTREMELY threatening to these alien predators as their main tool of control is through the mind; their worst worry is should humanity ever discover the truth and attain the same powers of the mind as they possess.
They preach a false concept of "peace" and "love" to disarm humanity and create a helpless/defenseless Earth. Their own convictions concerning this are made blatantly clear throughout the Christian bible where they are bringers of torture, suffering and death. The Book of Revelations / Apocalypse says it all.
The entity in many cases delivers negative prophesy. Most often, this predicts personal ruin, disaster for the victim, his/her loved ones or others who are close. The entity then offers false reassurance that it will remain with the victim through all of this, but does not lift a finger to stop it.
The entity in many cases, such as with ignorant (unknowing) New Age people, acts as a healer when channeled. As usual, no knowledge of any value is given and the healer as well as the patient remain cripples and are helpless without the entity's assistance, making them slaves.
I have dealt with these entities and they are anything but benevolent. They are bringers of death, misfortune and their victims of choice are childlike. People who get into angel magic are either extremely arrogant or their personal lives end up in disaster. One guy who was into this sort of thing was severly depressed and into drugs.