Hi!
A:
It's easy to get fast results if you don't care about your reads being atomic (*), and I find it hard to believe they've managed to get atomic reads without going through MySQL.
MySQL upper layers know nothing much about transactions, it is all engine-specific - BEGIN and COMMIT processing is deferred to table handlers. It would incredibly easy for them to implement repeatable read snapshots :) (if thats what you mean by atomic read)
(*) Among other possibilities, just use MyISAM.
How is that applicable to any discussion?
Domas