Can't understand "Transform Direction" output

Hi, quick question!

Why is Transform Direction node, when I feed it with Y=1, it gives me X=-1?

Here is my setup:

And here is an object preview:

And also the results (green is forward vector and red is transformed direction):

Why is that? Why isn’t the world axis the same as the results from this function?
How is it even possible that in all 4 directions it gives X or -X?!

I hope someone understands that better than me.

Well, for the record, I got an answer from Tommy on Discord. Forward Vector is not a world vector so that’s probably causing problems.