Unfortunately it is a fairly hypocritical message, given the problems that GNOME has created in KDE, especially forcing the introduction of CSD in the worst possible way. Even today, GNOME developers refuse to support the xdg-decoration standard to allow apps to request SSDs for better integration with DE.
Not to mention that Plasma relies on breeze-gtk to (try to) integrate GTK apps but now GTK developers say that themes are not supposed to exist and that the use of CSS stylesheet is just for internal use:
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