Though I haven't reproduce the issue on 9to5mac.com without Fission, this is probably a minimized test case which is able to reproduce the issue without Fission. You can't vertically overscroll the root element on red area. And interestingly, it's not horizontally overscrollable in the red area. I think this kind of cases commonly happen, that said, to fix this issue we will probably need to have the dominant axis scrolling, and even if the issue happens, users can scroll normally, and the issue is not so severe than issues that overscroll gets stuck, so I'd suggest this is an issue nice to have in MR1.
Bug 1702988 Comment 11 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
Though I haven't reproduced the issue on 9to5mac.com without Fission, this is probably a minimized test case which is able to reproduce the issue without Fission. You can't vertically overscroll the root element on red area. And interestingly, it's not horizontally overscrollable in the red area. I think this kind of cases commonly happen, that said, to fix this issue we will probably need to have the dominant axis scrolling, and even if the issue happens, users can scroll normally, and the issue is not so severe than issues that overscroll gets stuck, so I'd suggest this is an issue nice to have in MR1.