They are NOT suggesting downsizing, entirely sensible practice.

They say to sell everything except what can fit in one briefcase, and to buy all that stuff new in the new place.

Super time consuming and expensive.

I don't want someone's used bed or used sofa, so I'll have to buy new. Almost everything depreciates with time, so you're looking at a house of the good, usable stuff that can be sold or donated for a fraction of the price over the course of weeks (in the meanwhile you can wash your family clothes in the river and eat out), and then spend weeks buying brand new stuff (I'm not sure if either of you knows how much the household equipment costs).

You're both likely talking from the perspective of the single małe loving in the small furnished flat and moving to another furnished flat. In that one edge case selling everything and buying new may work.

(just don't move the goalposts: you're effectively discussing with the stance no one took, because no one was arguing downsizing)