Dragons are very confusing to me. I only know of the ones in the Abyss, personally. I hear stories about the ones and Astlan and they seem quite different. I don’t know anyone in the Abyss who’s talked to a dragon, but apparently people talk to the dragons in Astlan, or at least some dragons, sometimes, in some circumstances.
However, in both cases, the most common things is for the dragon to try and eat you.
I suppose if they ate enough humans they’d become familiar enough with them to shape change into them.
But the thing is, I am sure that if dragons can shapeshift, they aren’t telling anyone, for the same reasons demons don’t tell humans things like that.
That sort of knowledge causes widespread panic.
We really don’t want people making more mirrors like Tarlius had…that would be very inconvenient.