Without additional options it works because dh uses system() to execute
commands and it behaves differently with only one argument. I do not
think that this is a failure of debhelper because ocaml seems to be the
only sequence with command that has parameters, and I think it is hard to
use overrides for that "dh_ocamlinit -d".
I think the functionality of dh_ocamlinit -d should be split into a new
program, called for example dh_ocamlclean.