An extension seems to me like overkill for that. The can't go through undescribed doors rule is already in the Standard Rules. This is all you need:
The oak door is a privately-named undescribed door.
Understand "oak", "door" as the oak door when the oak door is described.
[ some insurance against inference or disambiguation prematurely revealing it ]
Does the player mean doing something to an undescribed thing that is not the player:
it is very unlikely.
[ replace with some real means of making it described... ]
Instead of thinking, now the oak door is described.