No Girls Allowed!

SC and H are searching the yard for boards.

"We are building a club house!"  They announce.  They gather the long, heavy boards in their arms.  Once they have what they are looking for they bring it over to the bamboo, a favorite hiding spot. 
They carefully arrange boards around the edges, blocking them inside.
"We're building a club house, right?"
"Yeah!  No girls allowed!"
AH walks by, heading this bold statement. Our eyes meet.  She asks me what HM and SC are working on, and I explain in plain terms.
"Well, that's a funny thing to do. I would like to build a club house too.  But everyone can come in mine." She said, thinking for a while. Instead of building, she remained nearby, watching the building progress.  A few other children came by to watch as well, and then moved along to the things that interested them.

"We need a sign!  Can I have some markers?" SC asks me.  I offer the ones which can be used outside and he sits down to work on writing, one of the first independent writing tasks I have ever seen him set for himself.

This new game is gathering attention, and soon various children stop by and ask if they can play.  SC and HM only say yes to the boys, and usually I gently remind children that it's Everybody or Nobody when it comes to play outside.   However, today no one seems too upset when they are being excluded.  I decided to see what would happen if I simply allowed this to play out. Some children are confused by the rules set for the club house, but most wander away to play their own game. It makes me wonder if the exclusion is less interesting than their own ideas.

Despite the language of the clubhouse, it is a quiet game, which begins to transition from building a structure, to a movement game.  EK joins and begins to lead a jumping game at the backdoor of the club house. The physical activity of the new game seems to be a natural transition away from their exploration into exclusion.

It has been a few weeks since that game has been played and I have not heard it explored again.  Did allowing this instance of specific exclusion to play out being enough satisfaction that it did not need to be tried again?
Did the connection between two friends mean more than the words they were saying?
Does our normal rule of Everybody or Nobody bring us the safety needed for more creativity, imagination and play to happen?