The code shows that we only load back to 4.0, but this still said 3.0.
* is the prefix configured when GTK+ was compiled (unless overridden by the
* `GTK_DATA_PREFIX` environment variable), and `VERSION` is the GTK+ version number.
* If no file is found for the current version, GTK+ tries older versions all the
- * way back to 3.0.
+ * way back to 4.0.
*
* In the same way, GTK+ tries to load a gtk-keys.css file for the current
* key theme, as defined by #GtkSettings:gtk-key-theme-name.