I actually think this is some sort of GNOME overall bug. It happens with GNOME 3, too, on my x64 machine: launch any application that inhibits screensaver. Naturally (and as expected), this now will block the automatic screen turn-off and lock screen while you still see your desktop. BUT if you now lock the screen manually, where GNOME 3 usually will turn it off after in seconds, it suddenly is shown forever - even though that makes absolutely no sense IMHO: the entire point of screensaver inhibit is to keep something visible like a video with with no user interaction, which of course already is a lost battle when the screen was locked (no video visible anymore then, is it?). Preventing a further power save via screen turn-off at this point just seems super pointless to me. Maybe preventing suspend actually makes sense so audio players can use it, but keeping the lock screen lit up feels like a conceptual bug/design mistake with only disadvantages.
So it might probably make sense to report it at https://gitlab.gnome.org/ but don't ask me for which subproject.
So it might probably make sense to report it at https://gitlab.gnome.org/ but don't ask me for which subproject.