So I asked a vapour barrier expert. His main job is to repair water
damaged homes. And he confirmed what my carpenter said. Best not to use
vapour barrier if you're building outside of code.

His rationale was that IF there ever is water damage, the vapour
barrier will hide it and prevent it from being noticeable on the
drywall. In the meantime the moisture will do a lot of damage to the
walls and end up costing a lot more to repair than had you noticed the
water damage on the drywall and gotten to it right away.

You learn something new. I've decided NOT to vapour my house in the
temperate climate of Victoria, BC. In colder climates, definitely use
vapour barrier.

Cheers,
Jack