[Groff] PIC misunderstanding?

[shaunjohnson . consultor]

Greetings,

I am probably being incredibly stupid but could someone please explain to
me
why the two pictures produced by the following fragment of PIC code are
different?
The second picture is the one I would expect.

Before anyone asks: yes, I have read the manual.

This is with GROFF 1.16.1 on Redhat Linux 6.2 for Intel.

   .PS 5in
   [
      move to (0,0)
      line to (1,1) -> "A"
   ]
   [
      move to (0,0)
      line to (-1, 1) -> "B"
   ]
   .PE

   .PS 5in

      move to (0,0)
      line to (1,1) -> "A"


      move to (0,0)
      line to (-1, 1) -> "B"

   .PE

Thanks,
    S.