They’re aspects of the same thing, but they’re very different. One is internal, a purely mental or visualization place. The other is external, somewhere you can actually go to via astral projection.
You didn’t do it wrong, but you approached it only through visualization, and that limits how it functions, like I mentioned above as in it doesn’t offer much of anything. That is for the one you astral project to it, then perform your workings (casting, healing, etc.) after astral projection.
If you try to do everything inside visualization without ever shifting into actual astral projection, you overload the cognitive and function of your mind. The mind is forced to sustain too much concentrated imagery and effort for too long, and it will start to strain and break down.
This is why people often report becoming unwell, depleted, or mentally fragmented when they insist on doing it all purely in a visualization mode. The issue is the lack of transition from a mental model to an astral projection.