When I export, the result of the code block is "X is Hello", but when I
use C-c
C-c to evaluate the block in emacs, I get "X is"--the variable isn't
defined.
This works for me on org 9.4.
I had trouble getting a file-level property to work across source blocks before, but it worked in a property drawer. I thought this was going to be that case, but I guess not. This seemed to work.