So looks like it's now displaying the overlay without the :before but it's a bit of the reverse, if you use CSS to try to hide the overlay, the overlay will still display.
We found to fix our existing sites using this approach, we had to turn OFF the overlay in settings and apply it manually w/CSS to any sections needing an overlay.
.Index-page--has-image, .Intro--has-image { background-color: rgba(255,255,255,.5) !important;}
If anyone finds anything else / can find how to hide overlay over just one section in an Index after SS's recent change, we're all ears!