it's likely suggested as an obvious thought experiment to help define a lower bound / upper bound versus alternative, not a policy recommendation.

In the Netherlands you used to be able to get a 105 percent mortgage, so you could finance the notary, transfer tax, mortgage advisor and so on. Nowadays it is at 100 percent and you have to pay for those services out of pocket.

No! He is advocating that 'mortage payment' != 'rent'

Costs to own roof over your head are in reality: mortgage + running costs + depreciation + cost of capital

Technically, it's the inability of the payer to pay the mortgage that causes market crashes.

If you had an oracle that could predict with 99% certainty whether a given housebuyer would make a certain size of mortgage payments, you could afford to lend them that amount no matter the size of the down-payment, with a 1% risk premium over your interest rate.

We don't have such an oracle, so we look for other signs. One of the signs of financial stability is the ability to pay a large fraction of the price in advance.

Sounds more like advocating for renting.