KT150s in a Preamp Design?

I'm a bit of a shade tree tube amp mechanic;  I'm no expert and have a decent but not comprehensive knowledge of design.  Can someone tell me what's going on with this tube preamplifier design?  I've never seen KT150s in a preamplifier!

http://www.thebestamp.com/Tube_Pre-Amps/Reference_Series/Reference-3.php

Calling Atmasphere!