The difference between lucid dreaming and astral projection is pretty easy to discern with practice. I doubt I'd ever confuse the two. But I often confuse being astral with being in the physical world.
How do you tell the difference between dreams and astral experiences? I don't know how to describe it. They just have different energy signatures. It's like knowing when you're soaking in water vs. on dry land. They feel different. It's similar to how I know whether my skin is wet or dry.
Physical reality is very dense and solid. Astral realities are less dense. If I touch a wall in physical reality, it feels solid to me, and it doesn't radiate much energy. It feels pretty much dead. But an astral wall is more energetic. It feels radiant and alive. It's less dense, so I can usually walk right through it. I usually avoid walking through astral walls because it feels too freaky, as if jello is oozing through the spaces between the molecules of my body. Even sticking my hand through an astral wall feels creepy.
There are lots of different astral realms, and some appear to be spectrally closer to the physical plane than others.
I suppose that if you could astral project and move around on the physical plane itself, you might be able to read something in another room and report it accurately, but I think it's more likely you'll see something different. Just because it looks like you're on the physical plane doesn't mean you are. If you're dialed in to a slightly different dimension, you'll probably pick up a message that doesn't match the one in physical reality.