dreamingincode

It does, it's called DocumentsUI and provides the system file picker. However its main entry point is often hidden, and imo it's still somewhat suboptimal/limited in certain aspects. But it's the only way to access the private Android/data directory right now.

Material Files also provides the ability to easily open DocumentsUI for browsing Android/data.

Material Files also allows you add a shortcut to the stock file manager (DocumentsUI), using "Add storage" > "Android/data" from app drawer. You may even manually edit the shortcut to point to a specific subdirectory inside Android/data, and I plan to make that easier (so that you don't need to manually URI-encode your path if you edit) in an upcoming version.

Yes, and this app adopted it as well. There's a toggle in app settings for Material 3 v.s. the old Material 2 right now, and there used to be one between Material 1 and 2.

Different design (Material 2 or 3 v.s. Material 1 mixed with Holo), different UX (e.g. multi-window v.s. dual-pane), Open source v.s. closed source, probably somewhat richer feature set from Total Commander (not entirely sure, didn't try it in depth).

Naming is hard, and I already have to implement file management :P

Just kidding. The reason is that I started the project mostly because I wanted a file manager with proper Material Design, and it's very unlikely that I (or AOSP) adopt a completely different design system.

It's the same for all file managers and the previous way of granting access is now patched via security fixes. If it's still working for you that's very likely because you granted the access before it was fixed, and if you move to a new phone you also likely won't be able to do that any more.