Actually making a battery user replaceable is not the same as returning to the old style (backs that can be removed without tools, rigid battery packs that you can carry a spare of in your pocket). I would say that a back that was held on by a couple of small screws or a series of clips, and any type of battery that is not glued in, would be "user replaceable". In fact a few years ago I replaced the battery in an iPhone 5 for someone and that was how it worked: 2 screws on the base released tabs that held the back on, lever it up (easy to do as the back was popping off due to a swollen battery!), detach the battery connector, attach the new one and reattach the back. There are people who would be afraid to undo a couple of screws or unplug a connector, but I would say that something like that would be reasonably described as "user replaceable" (but the moment you use glue to attach the back, meaning heat guns to remove it and no warranty once you do so, it would fail to meet that standard).