The Compare function in the Library mode is no longer functioning as it should. Clicking on the "lock" actually snychronizes the zoom. While trying to visually size two differnet lens focal lengths of the same scene to test image quality, I adjusted the Zoom slider so the two images each filled their side of the full screen view to show the same crop section of the scene. But clicking the lock icon caused one of the two images to change size to match the other's zoom percentage. After several attempts, it appears that "lock" and "Sync" now perform the same function. That's not what has previously happened and I'll bet is not what Adobe intended. Please fix this bug.
I've just tried this on Mac Catalina, and Lock zooms in both to the same zoom, but at the positions they were at. Sync forces them to the same position as well, so they're definitely not doing the same thing. However reading the help makes no mention of the zoom setting in the 'Link Focus' lock, so yes, there's probably a bug, but not that the lock and sync are doing the same thing.