See https://drafts.csswg.org/css-animations-2/#keyframes, step 5.4: "All logical properties are converted to their equivalent physical properties."
<rdar://problem/70579530>
Created attachment 451044 [details] Patch
Committed r289181 (246873@main): <https://commits.webkit.org/246873@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 451044 [details].
*** Bug 241784 has been marked as a duplicate of this bug. ***