No, Tibetan book of the dead is orthogonal to Buddha's teaching. People attempted to mix them but Buddha's teaching was only able to be correctly revealed in ea

No, Tibetan book of the dead is orthogonal to Buddha's teaching. People attempted to mix them but Buddha's teaching was only able to be correctly revealed in each detail by a Buddha due to only him having a high enough level to see things as they are (that's why he called himself a Tathagata), so people can't help but change it by adding their own thoughts and ideas. When we look at cases of a special teacher showing a reaction we must confirm every exact detail in context or we will likely completely miss some critical qualifying detail. Buddha didn't see the concepts which religions of the day promulgated so he didn't teach concepts from them. They were naturally imprecise or wrong in some ways. Each object and each living creature has its own self; for example an apple tree only makes apple fruits, and if it changes what is in itself due to a change in its environment then it's a fact that its own truth changed. People who are not enlightened can't see, so they make things complicated due to thinking and learning others' ideas without knowing the world. That's why someone who could actually see things - the enlightened being - had to come to the human world. No one expected what he told people. Most /wanted/ Atman to be a real thing - perhaps that's why Buddha was shunned while he was alive. Hope that makes some sense for you.