Sorta …
Some package needed xdg-desktop-portal (maybe … flatpak, for example)
xdg-desktop-portal has a number of dependencies too.
One of them is xdg-desktop-portal-imp which is not a real package, but will be fulfilled by any of the xdg desktop portal backend packages.
Here is an example output from my system
(in this case explicitly installing portal … but the result is the same)
$ sudo pacman -S xdg-desktop-portal
resolving dependencies...
:: There are 7 providers available for xdg-desktop-portal-impl:
:: Repository extra
1) xdg-desktop-portal-gnome 2) xdg-desktop-portal-gtk
3) xdg-desktop-portal-hyprland 4) xdg-desktop-portal-kde
5) xdg-desktop-portal-lxqt 6) xdg-desktop-portal-wlr
7) xdg-desktop-portal-xapp
Enter a number (default=1):
And so you see there the multiple options, but gnome being the automatic choice simply by virtue of being first in the list.
It is also possible that certain package managers or certain options could have obfuscated this selection.
(for example --noconfirm)