Yep, the Biscaya's are "All Season Polyester" athough they did produce the Biscaya 370 in both "Heavy Cotton" and "Polyester Rip Stop Nylon" as well as "All Season Polyester" 2007 season only.
Also the early "All Season Polyester" Biscaya's came with 28mm aluminium poles that had a wall thickness of just 1mm, subsequently there were reports of poles splitting on the larger models.
Since 2010 the Biscaya poles were upped to 1.5mm wall thickness the same as used for the Awaya.
Thankfully my 2007 Cotton Biscaya 370 came with 23mm steel poles, although the pole bag is dam heavy!