The Jolla specs are lukewarm only compared with android devices which gobble up any performance difference. They are very close to the high end compared to any other OS which doesn't have the overhead of a VM.

Neither WP, BB10 nor iOS is currently being shipped on a phone with more than 2 cores, BlackBerry has 2GB of ram but iOS and WP still have 1GB. And they clearly perform in the same ballpark with high-end androids. The iPhone 5 still has one of the best sunspider scores on mobile.

So it's not that they need to have a secret sauce to have high end experience on those specs. They just need to not mess it up.