Try this version: http://wpt.live/acid/acid3/test.html
edit: MacOS and Windows.
On FF for Android it hits 100% but the image is incorrect (there is red text in the top-left).
Same (FF 104.0.2 on Mac, with uBO).
The failing test is:
Test 64 failed: object.data isn't absoluteDisabling the LastPass add-on brought it to 100%. I'm guessing you also use LastPass?
Though I suppose rendering differences that affect z-order or visibility could be detected indirectly, by listening for pointer events on elements that are "supposed to be" visible/hidden.