I don’t know for sure but I would speculate that since the original Roblox file format was XML and parts were the most common content in a place, it was possibly an attempt to save file size. Though that’s a pretty weak reason.
I know for sure it doesn’t have anything to do with the rounding to FormFactor sizes (Brick / Plate) that parts used to do because the engine could load / save non-rounded size even back in the early days, only scripting blocked non-round sizes.
I’m not sure I ever fully understood the difference between the old “Live” and “Pending” labels, especially when certain items seemed to appear in multiple weeks of release notes.
This looks to be a good change for clarity! Correct me if I’m wrong, but my assumption is items in the “Current release” tab have officially made it to “live” production (studio, client, etc.), items in the “Pending release” tab will be moved over to “Current release” if/once they’re approved (staying in “Pending release” until then), and “Recent releases” is book-keeping of what made it into each “Current release” prior to the start of a new release cycle.