The argument is probably something along the lines of "most building codes are costly but not necessary for safety" aka "it can be somehow done significantly cheaper but just as safely, a way that doesn't follow the building codes".

Not sure such a way exists...

Are you in favor of bulldozing favelas in places like Brazil if the inhabitants can't afford to fix their shanty to meet up to code?

I guess it comes down to comparing the risk of poor quality housing vs the risks of homelessness. Kind of like that saying "the real minimum wage is zero"

For many of those people, it's not a risk of homelessness but rather that they would have to rent someplace outside the favela at a much higher price, one they may be able to barely afford. Sort of like in the US, where zoning/building don't generally make people homeless but instead put a person into the situation of the favela dweller who has the option to rent while paying a large portion of their income, except without the option to build their own sub-code housing.