A pre-mine doesn't stop being a pre-mine after you've sold it and lined your pockets with the proceeds. When they eventually finish[1] dumping the rest of their coins on misguided members of the public will the pre-mine be 0%? Obviously not.
Moreover, the self same people made purchases in the "crowdsale" and then immediately paid those funds back to themselves. E.g. Hoskinson extracted a million dollars the day the presale closed.
> the stake of the founders, including the non-profit Ethereum Foundation, was 11%
Check your math because 12 million out of 72 million isn't 11%... nor does that include the additional funds 'purchased' in their share offerings (in scare-quotes because it's not really correct to call something a purchase when it was paid back).
Ethereum was 100% pre-mined. They then sold about ~80% of the pre-mine to the public (and to themselves, with no known upper-bound on percentage of the self-sales) and pocketed the proceeds. After that they issued additional coins via mining to the public and diluted their positions but later substantially cut the supply of mining off when the price kept falling. The plan now is to soon eliminate the mining and award the coins that would have been mined to existing large position holders (parties with more than $20k worth of ethereum).
When this transition is complete the issuance will be extremely similar to ripple's -- e.g. a huge amount created by the system's operator, a large portion sold by that operator to the public over time, and a portion given away as lotteries. The primary difference is that in ethereum the lottery part was conducted directly by the system through diluting the operators shares rather than being handed out in airdrops as Ripple did, and -- of course-- the relative amounts of these groups. Ripple has been a lot greedier about it.
[1] Technically they'll never finish, because of the more recent plans to continue to award these massive pre-mine holders with additional coins in perpetuity in exchange for taking them out of circulation, they'll be able to largely preserve their position while continuing to dump on the public.