Bug#903836: pcmanfm-qt: Depends transitively on libgtk2.0-0
pcmanfm-qt doesn't depend on GTK. It neither depends on libfm anymore -- the latest version of libfm-qt is independent of libfm. pcmanfm-qt uses Qt for its GUI (and some other things) and GLib for its file management because GLib is better than Qt when it comes to file management. GTK depends on GLib but not conversely. So, pcmanfm-qt has nothing to do with GTK, whether directly or indirectly.
Bug#903836: pcmanfm-qt: Depends transitively on libgtk2.0-0
And by "latest version", I meant the latest git version. It'll take a while until it's released. However, even its old versions never depended on GTK but only on GLib.