You misunderstand the nature of the ISO 8601 standard; it’s not a format meant for human consumption, it’s a serialization format, for exchanging data across machines and for accurately storing dates, times, and periods. The full ISO 8601 standard would be unreadable for anybody.
If you want Nautilus to use a YYYY-mm-dd HH:MM:SS format (which is not valid ISO 8601) then you should read the previous topic on this.