The point was that the premium was lower so you could save the difference and instead of that difference going to waste each year, it could compound over time.
I mean, if a HDHP plan costs 400 / mo and a regular plan costs 1000 / mo, you get to save the 600 and let that compound over many years (if you don't use it), rather than lose the 600 in insurance premiums.
tathougies was referring to the difference in monthly health insurance premiums. I don't see what their comment has to do with Flexible Savings Accounts.
From what I understand, even the HDHPs have such high premiums that the point is not being achieved, especially if you have to go through the marketplace rather than the employer.
Due to rising healthcare costs, and employers reducing the portion of health insurance premiums that they want to pay for their employee (aka a paycut), that's going to be true regardless of HDHP or not HDHP.
Not that they shouldn't do it, but a slight paradox there.