If you ask to have your visa processed separately without waiting, they will do it.
I don't know what would happen if he had a visa pending, not decided, and tried to enter NZ as a visitor. I THINK it might cause difficulties. In your place, I would contact INZ and ask the question - but don't be surprised if they say he would have to wait outside the country. (The objection would be that a visitor is, by definition, somebody who stays for a certain length of time and then leaves the country to go home again. By applying for a partner-sponsored temporary work visa, he has signalled himself as NOT wishing to leave NZ, but to live and work there, so he's not a bona fide visitor.)