The clinical AT (probably determined by onset of blood lactate? how did they determine it) is different from what bicyclers have been calling their AT for years. What we're used to calling AT we usually determine by timetrialing for some distance or time (often around 30 minutes ala Friel) and using an average HR. This is liable to be above the clinical heart rates.
Here's a link to a helpful thread on another board. Note that the informative poster is a professional cycle coach. The RST folks post often in that forum, but you've got to wade through a lot of lame polls (not to mention uninformed speculation and magical thinking - the bane of the internet forum) to get to anything really informative.
You might also want to read through some of the articles and Q/A
here. The folks answering questions at cyclingnews are coaches and doctors with an understanding of both physiology and endurance training. I've learned a lot there, including that a lot of what I thought I knew was wrong. Not to mention that biochemistry is complex and not completely understood.