Directory configuration files with the same name do not get masked
Most software I have seen that has /usr/share/foo.d/.conf and /etc/foo.d/.conf configuration files ignores the /usr version of same-named files. 
~/.config/pipewire/pipewire.d/10-autostart-session-manager.conf should mask
This issue is particularly pronounced when a non-systemd distribution wants to autostart a session manager by shipping a file in /usr, and the end user wants to handle supervision of the session manager in a non-standard way. The user has no way to override the distribution, because any subsequent
context.exec declarations get appended.
 sysctl.d, modprobe.d, udev/rules.d all behave like this