Because Vector already applies styled to both .oo-ui-windowManager/.oo-ui-defaultOverlay and #mw-teleport-target that override font size, the changes in that task will cause the font size adjustment to apply twice for OOUI dialogs/dropdowns, making the final font size smaller than expected. Therefore, unlike all other skins, this change needs to be done at the same time as T348286: Move the default OOUI overlay and window manager inside the MediaWiki teleport target (in the same WMF branch).
The changes should be tested with legacy Vector, Vector 2022, and Vector Zebra (unless those two are consolidated before anyone gets around to this task).