There's an objection here when you get to tiny numbers, but surely you wouldn't get ice cream if there was a 10+% chance to get hit by a car?

I think he's saying that >1% or even >10% chunk of your probability mass should be on superintelligence, otherwise you're implicily >99% confident of stalled progress, which seems overconfident. We're not talking about not some infinitesimal fraction here.