kvantum-manjaro has a dependency kvantum, obviously. You can’t install a theme without the theming engine, lol.
so no, it was not. In the beginning of the topic is explained what is what.
ADDON EDIT:
I am glad that someone decided to revert the change since of today and the theme is againg a dependency by default. It is only logical, if you provide a xfce desktop with matcha-gtk-theme by default, and installed kvantum and qt5ct by default, to provide a matching visual appearance in the qt apps. Otherwise a novice user will either think “manjaro xfce is ugly inconsistent” wenn he runs his first qt app, or post a topic “how to fix” and always receive the answer, “yeah we know, now install this”.
The inconsistency with the gtk4 dark theme (the missing theme) is bad enough, maybe it is time to fix that too in the default config, since the manjaro team is actively developing (pamac) for gtk4? Shouldn’t be that hard to clone a file or 2 with another name in the system path, as i did in my .config. Maybe make adv-gtk4 package and a dependency of pamac, exactly as adv-gtk3 now works?