The fonts have some differences, but I'd have to agree with you the changes are so subtle it's hard to believe they resulted from an attempt to make a _radically_ new typeface.
[1] https://www.arun.is/blog/custom-typefaces/unique_typefaces_m...
Also many of these look like they just adjusted the weight ever so slightly. With variable fonts, I'm curious how this come into play when considering copyrights.
https://www.bitlaw.com/source/37cfr/202_1.html
Note that although the design of the typeface is not copyrightable, the computer programs which generate typefaces (‘fonts’) contain elements which are:
When discussing copyright "font" doesn't refer to the shapes of the letters (which comprise a "typeface") but the programmatic implementation of that typeface, which has been held to involve independent creativity. So if you take an existing vector font file, and alter the control points, you've created a derived work.
The situation is different in many other countries, which do allow for a copyright in a typeface. Generally the term of copyright is much less for a typeface than for many other works.
For example, I never really liked when Apple switched from Lucida Grande as the main UI Font to Helvetica, and I was very relieved when they replaced Helvetica with San Francisco.
I think San Francisco is a decent UI font -- it's much better than Helvetica. I don't particularly like it, but at least it doesn't annoy me.
The differences are subtle. If you show me short strings I probably wouldn't know them apart, but changing the font for the whole UI has a big effect.