Queue or no queue

I am confused about the queues for the Worlds.
Why is it that sometimes a queue appears when the world is full and MOST of the time, a message appears saying World is full and try again.

It would have been fine if a queue appears all the time when the world is full, then we would just wait for our turn. But when there is no queue, we would just keep clicking and trying and trying which is way more annoying.

So what is the normal behaviour, having a queue or not?

because the queue for any single world is only so big, and so if its full it auto kicks any new players trying to enter. when it lets in some of those waiting, it opens new spots and so if you get in when it does this, you get the queue other wise you get the other message.

ah I see. so even the queue is full...

Surely this mean we need a queue to enter the queue