I don't know that there were relevant changes between the advent of each, so much as kqueue just didn't have existing features in mind. I assume GP is referring

I don't know that there were relevant changes between the advent of each, so much as kqueue just didn't have existing features in mind. I assume GP is referring to the ring buffer design and/or completion-based processing, as part of the ability to batch syscall processing. This is reminiscent of external work like FlexSC and can be viewed as mechanical sympathy.