I'd guess that'd be water coming through the seams rather than saturating the outer and liner (which I assume was your standard waterproof tarp...). It looks like they've replaced the liners with xpac now, should make things a bit lighter but if any water does get in, it won't drain.
I had the same thing happen with my Apidura saddlebag during a long day of pouring rain/riding through streams. Soaked through seams and puddled at the bottom.
Which Swift bag did you pick up/what are you using it for, thought the 2(?) GB bags would have you covered...
I'd guess that'd be water coming through the seams rather than saturating the outer and liner (which I assume was your standard waterproof tarp...). It looks like they've replaced the liners with xpac now, should make things a bit lighter but if any water does get in, it won't drain.