The general premise still holds though - As long as the pre-money in a round exceeds the post-money in the prior one, the owners are worth more. The analysis is over-simplified, but it still explains the situation clearly.
As for how much is given away... I think Cloudera is a special company. Most of the unicorns are. The same strength ("We can wait on the money") that gets them to a billion is also what allows them to get away with less dilution.
Of course. But it's post in one versus pre in the following. If the post-money valuation grows from 50 to 60 million after taking in 20mm in new money, the founders get diluted. If it grows from 50 to 60 with 5mm in new money, they don't.
As for how much is given away... I think Cloudera is a special company. Most of the unicorns are. The same strength ("We can wait on the money") that gets them to a billion is also what allows them to get away with less dilution.