I've been reading this thread with abject fascination. I get why some are frustrated by the idea of being made to wait for content. Some feel patronized. Others simply don't want to wait. But what I can't understand is the people saying that this is arbitrary or serves no purpose.
Of course it serves a purpose: it encourages players to learn to make stages gradually, beginning with the basic building blocks (literally) and upping the complexity in a controlled manner. I consider myself to be an intelligent, independent, well-adjusted adult, and I have no real problem with this approach. I'm not a level-designer by trade, after all. I appreciate the structure. Not everyone has to, but to say this is arbitrary or lacks any sort of redeeming quality is a bit unfair.
The way I see it, this approach seeks to accomplish a couple of things, some of which have been mentioned already:
1. It encourages players to experiment with all of the tools rather than sticking to a relative few. Most of us have likely experienced this phenomenon before: give people a universe of options and many will simply stick to what's safe and familiar.
2. It encourages players to learn the basics of creating a level before descending into Kaizo inspired madness. This could lead to higher quality over all, although this remains to be seen of course.
3. Relatedly, it ensures that there will be a range of different level types and difficulties -- from simple to complex, and from easy to hard. This is a very good thing for new players. It ensures that these players will always have a healthy amount of levels that they can play through and enjoy as they become better at the game, while experienced players will still have all the diabolical levels they can stomach.
I think it's actually a pretty smart way to go about things. The alternatives seem either easily exploitable or contrived. A level requirement will encourage slapdash designs in the rush to unlock content. A system that measures "skill" sounds good on paper, but how do you quantify that exactly? Some have said that it should be based on hours actually played, but that has its own problems. Not everyone has the time to play a game for even an hour a day. For these people unlocking everything could take even longer than 9 days, depending on how the unlocks are structured. Tutorials are boring even in bombastic action games -- what makes people think that they would be more palatable or effective here? A complicated tutorial would be a turn-off for many gamers and reviewers, and a simple one would defeat the purpose entirely.