OK my friends...
Astral projection is much more difficult to achieve than mental projection.
But the problem is that you need to master astral projections first before you will also get opportunity to have mental projections.
Why is that so I don't know, but probably it is because flying is easier than levitating, but you first need to levitate before start flying.
Astral and mental projections are different.
I had had many AP over many years before I realised that mental projection is something completely different.
What I have written is from my own experience only, so I would not dare to generalise.
Anyway, I would like if you could add something more about this subject.