i read that too, but it was in relation to unfermented sauce. some folks just blend up a bunch of raw peppers (and other stuff) and cook the mush, so the pH of the sauce is the same as any veggie - i.e. prone to rotting - hence the need for pickling.I believe vinegar is primarily added to adjust the pH of your finished sauce below 4.5 for it to be shelf stable,
i haven't tested the pH of my hot sauces nor the brine (will do next time). however, i'm pretty confident the pH was below 4.5. lacto can take a kettle sour down to the low 3's in 24 hours, so despite the lack of 100*F heat i'd be shocked if it wasn't taken down to at least 4. while our hot sauces aren't kept warm like a kettle sour, they do have the benefit of time. i let me sauces ferment for 4 to 6 weeks.
in the context of fermented hot sauces, i read was that the use of vinegar was a preference thing: some like it, some don't (they pejoratively refer to such sauce as "vinegar bombs"). the author recommended using apple cider vinegar with fruity hot sauces, personally i think it works best with a more "straight-up" hot sauce - the vinegar tang does a good job of taking the place of the fruitiness, IMO. definitely need to play around more with the fruity/strong flavor vs. vinegar thing, and also adding different amounts of vinegar vs. brine.
for my sauces, i need to add some sort of liquid when i blend otherwise the sauce turns out way too thick. i wonder what other liquids could be used... beer? wine? spirits? acidic fruit juice? coffee?!?more so than it is to adjust the flavor or viscosity of the finished sauce.
if you end up testing the pH of your sauce and/or brine, please post the results here. i'm currently sitting on about a dozen bottles of hot sauce so might be a little while before i set up another batch...I'm hoping to avoid using vinegar where I can because it does have a tendency to overpower other flavors, but I'll use it to adjust pH if necessary.