I have two units that are heated by heat pumps in Massachusetts.

One has mini splits. You definitely don’t generally put mini splits in every single room (like bathrooms or interior hallways) because each mini split requires tubing, is large, and expensive. No, I think it’s way more likely that you would have them in the bedrooms rather than the hallway

In New Zealand I have seen small heatpumps in bedrooms, but I would have to say it is extremely rare.

But we have many very toasty hallways leading to cold single glazed bedrooms!

That might be a climate difference — it gets below 0 Fahrenheit here every winter, as I understand it, NZ is quite a bit warmer, so maybe the strategy of “heat the core of the house and let it radiate out” works.

There are historical and cultural reasons for our poorly insulated and heated homes, but "heating the core" is not one of them.

In the last few years the central govt has brought in legislation requiring landlords to heat and insulate homes to a certain standard.

Exactly. In this example, which is pretty common here, I installed 1 in the living area and then 1 in each of the bedrooms.