Play all but one rule is into play. What if play one extra card rule is also in play?
Since the dutch fluxx card says "the one with the most keepers can play one more card" (as opposed to must play one more card) then it would be that player's choice if they want to play the last card or not.

The key is in the compulsion, since "can" is not compulsory. It is possible that the wording in dutch has different compulsory connotations, but based on the English translation, I can only conclude that it is not required.