I realize this; however, at the time I (and many others) was of the opinion that encounter guidelines didn't work at high levels / CRs anyway. They plan was to implement a new encounter building guideline as well.
However, I have abandon the approach taken in this thread and my
5e Hardcore Monster Manual thread. That is one reason I started the
Mythic Monster Updates thread. I have ran a Kickstarter last year for Immortal rules:
Ascension, the Codex of Immortals, which will be published early next month.
In the future, my "epic" monsters will use the standard DMG guidelines, mythic templates from Theros, or my custom "exalted" monster rules from Ascension. These stat blocks are a few years old at this point.
EDIT: If you read the OP, it explains that the assumption is that the encounter guidelines are wrong. If I remember correctly.