The issue's primarily addressing distros and projects that ship their own GTK themes as default to users, like Ubuntu and Elementary and System76. My wife's desktop runs Ubuntu, and if something doesn't look right, she doesn't even know she's running something called GNOME - she just knows that the problem is with software (OS, desktop environment, kernel, video drivers, GTK style sheet, whatever).
Most people aren't going to blame GNOME for broken style sheets, they'll be blaming the creator of the style sheet, whether they know what GNOME and GTK is or not.
The issue's primarily addressing distros and projects that ship their own GTK themes as default to users, like Ubuntu and Elementary and System76. My wife's desktop runs Ubuntu, and if something doesn't look right, she doesn't even know she's running something called GNOME - she just knows that the problem is with software (OS, desktop environment, kernel, video drivers, GTK style sheet, whatever).
Most people aren't going to blame GNOME for broken style sheets, they'll be blaming the creator of the style sheet, whether they know what GNOME and GTK is or not.