When a snapping scroll area is created, post layout snapping always forces the container to the first snap position. This happens even when the container is right-to-left (the last horizontal snap positions is closest to the origin) and when the first snap position shouldn't be active because of proximity.
Created attachment 430720 [details] Patch
Created attachment 430728 [details] Patch
<rdar://problem/79184230>
Committed r278862 (238806@main): <https://commits.webkit.org/238806@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 430728 [details].