Does this even make sense to you? I acknowledge I am not an experienced Linux user yet, but this seems most weird to me; why would KDE Plasma offer me to update GNOME?
For context, I am using Debian 13 Stable, which I installed just with KDE Plasma - so I’m not running more than one DE, nor did I install more than this.
The GNOME platform application is used by flatpaks. Basically, a flatpak can be built against/designed to be used with a specific visual toolkit. To do that, it needs to download specific parts of that toolkit, which is what you’re seeing.