Proposed by @mounirlamouri on the corresponding blink-dev intent-to-prototype thread. I am moving the discussion to GitHub.

The summary is that Mounir wants to treat display as legacy (providing a mechanism to continue supporting it as a fallback for legacy browsers, but gradually fade it out), with a new display fallback list being the new way to specify display. (As opposed to the current proposal, which keeps display as the end of the fallback chain, with display_override being a list of things to try before falling back to display.)

Mounir's plan would make display eventually obsolete, while Daniel's current plan would keep display as part of the algorithm forever.

Details are in the above thread.