Oh, I see now. Yes, I would agree. I doubt the game designers gave any real thought to the possibility that 4 tiny creatures would be in one space, and 4 other tiny creatures hostile to the first 4 tiny creatures would be in another space, and neither side could melee with the other until one of the tiny creatures "made room" for the enemy.
That really has nothing to do with the topic of this thread, but it is a correct observation. I'd say it's (obviously) a situation ripe for DM adjudication. Personally, I'd allow the first tiny creature to enter the enemy square (provoking four AoOs), and if it survived long enough to attack, force it to return to its original square after resolving the attack. But that's just my solution to the problem, not RAW.