The S3 mkii is really nice sounding speaker, but I personally did not think they sound at all like ESLs. YG's more ethereal sound is closer. I love the sealed enclosure; more manufacturers should use them, in my strong opinion. To be picky he misused "high-pass" but glad he at least went over positioning some.
The ESLs have a sound of their own (with their own set of problems). I think that what he meant is certain lack of obvious ('cos some certainly exist) box colorations that set those speakers appart from more conventional designs using MDF box.