MTR section 6.4 (Extended Format Deck Construction) looks to have been partially erased. Obviously Extended isn't a thing anymore, so I assume the entire thing is being axed.
I suspect that this continues to exist because of the brief overlap between the publication of the most recent documents, the release of Theros, and those few events still in the pipe. Most likely, the format and the section will either be eliminated or tacked on for a while as an appendix or noted as a viable casual format.