a) Solution X does it generally better than Y and their solution is *ported*.
b) Adapt to solution Y. The end.
Most of the time it is b. Because Vim shall not be Emacs. Linux shall not be Windows. And macOS shall not be Windows either.Do you remember that foolish Windows-Themes on Linux? Luckily GNOME has killed custom theming. And Apple also. Custom theming is a horrible mess aside from areas where it is intentionally (e.g. Vim color schemes).
But it is also possible that Gimp moves to option A. At some point and they are interested in user-interface improvements. Most people just want to use Single-Window-Mode which shall be default for many years.