4444 says that "hold short" means:
"to hold not closer to a runway
than specified in Part V, 10.3."
Part V, 10.3 says:
"Except as provided in 10.3.1 or as prescribed by
the appropriate ATS authority, aircraft shall not be held closer
to the runway-in-use than at a runway-holding position."
So it doesn't specify whether you should stop at Cat 1 or Cat 2/3 bars... but if in doubt!