Adam,

I think this explains what is going on[1]. Basically, both Debian ships it's own
version of start-stop-daemon in dpkg and the arguments are different from the
Openrc implementation. See man start-stop-daemon(8).

This is definitely a Debian bug; please submit a report there. It maybe that
patching sh/start-stop-daemon is the right fix in Debian as it can only be
calling dpkg's s-s-d.

Thanks

Mark

[1] https://github.com/OpenRC/openrc/issues/383