The argument that China consumes a set amount (of any product...

The argument that China consumes a set amount (of any product they import), and that they are going to import it anyway, is certainly valid. The question is who they will import it from.

Growing Chinese economy over the past while created a strong middle class. That middle class can afford and is willing to pay a premium for Australian, NZ, and other western products which for factual, cultural, and marketing reasons they see as superior. The trade war weakens this middle class, and over time they may begin looking for cheaper alternatives to source that "set" amount (i.e. importing from places where labour and thus products are cheaper).

So I guess in the long run (not talking about today or tomorrow), if things are not resolved, domestic products or those from other emerging economies can replace Australian and NZ products in Chinese market.

Personally I think, things will resolve, as both nations can't afford the consequences. Worst case, things may drag on for a while until Don the toddler (and IMO the biggest insider trader) finishes the rest of his short time in WH.