There will be people here that know way more about Stephensons than I do - but they really are both legendary and an institution in the niche outdoor gear scene in the US : - Stephensons Warmlite being a kind of 'sine non quo' of "expensive but fantastic".
The home-made website you're mentioning has had a huge revamp since last I looked - it's way 'slicker' than it was (!)
I believe they are a family of nudists or 'naturists' - possibly explaining why one photo shows naked women entering sleeping bags. ie - it's a naturist thing, not a pervy marketing ploy (I think).
People who have used their gear often seem to swear by it - *really, really* enthusiastically.
This could be on account of needing to defend the huge dollar amounts they've parted with in order to acquire said gear - or it could be because it really is that good.
I don't know for sure, as I own none of it. Meh.
But i have spent untold hours attempting to decipher their somewhat cryptic explanations of Vapour Barrier clothing. Vapour Barrier being one of the Stephensons central design tenets.
I don't know that they are much interested in 'reaching the masses' - I had someone tell me that they were kept flat-out ('and quite profitable thank-you-very-much') from their very 'bespoke' approach to outdoor gear.
Young Bill Stephenson (in your link) certainly does have a beard on him doesn't he ? Extraordinary.
Someone here will have some less frivolous info on Stephensons for sure.
Cue less frivolous person..