Interesting stuff.

When I was shopping for an inground pool back in 2003 I got quotes from 3 different pool companies. Two offered designs that included a main drain and one offered a design that had a return at the bottom of the deep end rather than a main drain.

I'd never heard of a pool without a main drain so I thought the company that didn't include one was cutting corners to increase profit (their pool was a little more expensive than the others). So we ended up with a design that included a main drain.

Based on the links provided it seems the company who didn't install main drains was on to something.