The only policy area Labour has any real interest and skill in is workers rights (and even then: income insurance? Really?) In other key areas - income inequality, tax policy, climate change, industrial policy - they just follow the Greens. Green policy one election tends to become Labour policy at the next one (and, if the public is won over, National policy after that - see home insulation schemes, or the bright-line test). And partly this is a victory by default: Labour's perpetual cowardice and fear of criticism means they're too chickenshit to put their own ideas out there, so the Green ones become the de facto left solution because Labour isn't offering any alternative.
Which makes the stuff about the Greens wagging the Labour dog amusing. They're already wagging that dog - just very slowly.
Obviously, as a Green voter, I would welcome speeding up that process. The more MPs the Greens and Te Pāti Māori bring to a left coalition, the louder their voices will be, and the more Labour will have to give them. But also, I want them to play hardball on this. Which will admittedly be easier if Labour doesn't have any agenda of its own.
As for Labour concern that the prospect of Green-led policy could drive voters to National, that sounds like a "you" problem. It also sounds untrue, given public attitudes towards wealth taxes and higher public spending. In fact, in light of those polls, one might also call it an elite lie to deter change to the status quo. But either way, Labour's solution is obvious: if it doesn't want people to think it will adopt Green policy by default, get some of your own, and stop whining that people expect you to actually stand for something.