Williamson's anonymous hiking partner provided some additional information, stressing the importance of staying on the true PCT in any speed record attempt. Further discussion of "style" is further down this thread:
One thing I would like to stress as well for anyone that hopes to challenge the record is that they need to be on the PCT every step of the way. In 2005 when Horton ran the PCT he took the detour around Glacier Peak where Scott and I didn't. This is significant as it takes a road out of the equation (no resupply for runners) and adds 10 miles of old growth blow down to crawl over. In addition about 5-6 glacial melt streams that must be forded. There is no doubt in my mind this adds significant difficulty over the reroute road option. Also in the past some of the PCT speed records have taken alternates to avoid fires etc. I would stress that Scott and I walked the entire PCT and I think if anyone wants to claim a PCT speed record in the future they would need to be on the PCT for the duration of the trip.
http://fastestknowntime.proboards.com/thread/29/pacific-crest-trail-ca-wa?page=1