> I haven’t found that to be the case, what improper behavior did you see? (I’m asking because I’ll file an issue if it’s actually wrong and if you don’t feel inclined to file it yourself)
When scrolling through a long document with a touchpad, it's natural to make several swipes in rapid succession, with the second swipe starting before the momentum scrolling or snap animation triggered at the end of the first swipe has finished. On my Mac, in Chrome it appears that starting the second swipe interrupts the snap animation (good) and doesn't start a new one when the second swipe ends (bad), even for a mandatory snap container—leaving the container in what should be an impossible steady-state.
In Safari, things seem to work as expected, except for the more general usability problem that making multiple swipes like this can cause the scrolling to be amplified far beyond what the user would expect for a non-snapping container.
In Firefox, things mostly work, but I'm occasionally seeing instances where the container below the one I'm scrolling also scrolls a bit. Not easily reproduceable, but since I was playing with the horizontal scroll container examples it seems unlikely that I accidentally made the right combination of one and two finger gestures to get the cursor to stray down to the lower container, scroll it a bit, move the cursor back up, and continue scrolling that one. Ordinarily, no amount of frantic two-finger swiping results in that much one-finger cursor movement, and it appeared the spurious scrolling of the second container was more correlated with rubber-band animation when scrolling past the end.
And that's from about two minutes of playing with literally the first example I could find.