OK, quick Q: does it appear on envelopes as

77 Baynhams Drive
Hawk House
[Wolvercote]
OXFORD

or

77 Hawk House
Baynhams Drive
[Wolvercote]
OXFORD

or something even weirder?

I think the addr:interpolation really needed to be removed from the building outline. addr:interpolation is just not allowed on closed ways, and is meaningless without nodes on it containing addresses.

Although, IMO, an interpolation is needed for big apartment blocks sometimes because there can be absolutely loads of addresses, and it'd be hellish to do them with comma-separated addr:flats or addr:housenumber.

-------------------8<------------------

So how to do it right? The best way might be to tie it down to entrance locations, one way or another. That's kinda meaningful to users because it tells you where to walk and/or what doorbell to ring straight away:

- https://www.openstreetmap.org/?mlat=51.77122&mlon=-1.21397#map=19/51.77122/-1.21397 (lots of addresses per entrance, so use an interpolation)

- or https://www.openstreetmap.org/?mlat=51.76531&mlon=-1.20268#map=19/51.76531/-1.20268 (only 3 addresses per entrance, so comma-separated is fine)

- the even wackier situation with Cavalier Court, where there's different continuous runs on different levels, presumably corridors: https://www.openstreetmap.org/way/129003603#map=19/51.76858/-1.22687&layers=D

addr:*s are ultimately just an attempt to physically locate the delivery endpoint, however it's done.