...Just wondering, but if I start using this for a project I'm well into, will certain things not work correctly like how you see in much older builds of Classic?
—, in the unlikely scenario that your project depends on line object collision being bounding box. The general consensus was that this was mostly useless for the line object, so it's not an option, the only collision type now is angled_box. The panel, box, and sprite objects still have the option for bounding box collision.
The only other problem I can see is if you had panel objects that you purposefully misplaced because of the old bug, so they would appear in the right place, you'll have to move them to where they are actually supposed to be.