For now I will cease beating a dead horse on most of your concerns. I have either made my point or there's little hope.
"You have people getting sick on one trip and thrus never getting sick despite months drinking untreated water everyday. "
As for your quote above, that's to be expected. 2/3 of people who get giardiasis, more or less, are asymptomatic. There are people who can beat the odds at just about anything.
Scott Williamson, Mr PCT himself: Williamson does not filter or treat his water. 'I’ve been sick multiple times, I have had giardia…' (and then he ticks off a list of other parasites, but your trusty reporter was too dumbfounded to write them all down).'I am very selective about my water. If it looks like a heavily used area I will try to find cleaner water, but I have had to drink some nasty water. It saves time, I just dip and drink.' He does add, 'If you don’t want to be sick at some point, you have to always treat your water.'
I know some people will say cherry-picked, anecdotal, biased. Yet it is another piece of powerful evidence backing up the peer-reviewed science.