Well, I'd expect that if they allowed 5v through but with a low current limit (I think the default 5v standard states quite a low current allowance). They could catch anything drawing too much and shut the port off until it detects disconnection/other reset.

I mean, if they're thinking about protecting a downstream device, adding this logic would make more sense than just not supplying any power unless a negotiation is made.

In any case, since standard USB ports on a computer will output 5v without anything being negotiated, then it's really no less safe than any other USB port in that regard.