The Navy/USMC wrote themselves a Specification they cannot meet.
Or, that they revised. Take a look at what happened to Paladin and Crusader in the field artillery world. Every so often, the requirement that has been the bedrock of an acquisition program .... changes.
(The USN's helicopter minesweeping capability is one such)
Also, FWIW, "Beachhead' seems to have become a word that is used less and less often in expeditionary warfare.
Put another way, they've changed their minds, and in a different way, have made an argument that "they have changed with the times."
Not sure that's an airtight argument, but it is usable.