I hadn't heard of this, but it sounds like it comes from the Theosophist's misunderstanding of an emanation body (nirmanakaya) in Vajrayana Buddhism. There's a reason why many of the practices in Vajrayana are taught progressively and under guidance, and that's mainly because confusion and misunderstanding can arise when not grounded in proper view (samyagdrishti), which can have a very real and direct impact on a person's mind. But from what I can tell this western practice is completely divergent from anything found in the kangyur or tengyur.
Have you considered talking to a Vajrayana teacher to help understand what's going on? Tergar has an ongoing teaching this year on Buddhist psychology [1]. Also, a teacher I practice with posts most of our sessions online for free as well [2].
If I'm not really with strong determination for cultivating a Vajrayana practice, do you think I can still benefit much? It's just these "introjects" that bother me or maybe what you called it.
I think it'd be perfectly fine to engage with a Vajrayana teacher to see if it helps with what you're experiencing, there's no requirement to be initiated into a lineage and take practice vows or anything like that.
The only reason I mentioned a Vajrayana teacher rather than a western psychologist or even a teacher from other Buddhist schools is that these advanced visualization practices are something most Vajrayana teachers will have experience guiding students through. Which also means they'll be well versed in what to do when things go wrong.
Have you considered talking to a Vajrayana teacher to help understand what's going on? Tergar has an ongoing teaching this year on Buddhist psychology [1]. Also, a teacher I practice with posts most of our sessions online for free as well [2].
[1] https://vajrayana.tergar.org/buddhist-psychology [2] https://www.youtube.com/@ThuptenPhuntsok