Assuming you're right, then that fear is about money, if your claim stands right. But, if the fear is money, why don't they just let every developer test it early for a fee? Σ that up and you end up with a great way to fuel your startup, without causing premature investor-friction.

Here's a number: $ 5 × (100.000 × ¼) = $ 125.000 in Free Capital

What that means for their customers (Early Adaptors) is this: $ 5 + EULA + (Freemium of sorts in the future, for loyalty) = WIN

TBH: I thought the same, I mean the decision to lock-out so many potential developers willingly is very bad, or just ignorant. Personally I value their startup high as a replacement of <Enter-Mobile-Framework-Here>, but time is not everything, sometimes you can loose a lot of customers, because of the bad first impression you have made in the beginning.