So there will be formats that can reorder the chunks, and those minimum-viable readers will all break when they encounter a file from a different source, because they hardcoded a read order. This leads to an experience on the user's end where they need a "fixer" tool to reorder it to deal with the bad decoder.

There were tons of old binary formats that were like this. It can happen with text, but it's less likely to, because a larger proportion of textual formats build over a container like XML or JSON to offload the text parsing, and then they end up with some pre-structured data.