"Once it's in fullscreen mode, any touching or swiping, in any direction, causes it to drop out of fullscreen and back to the regular lightbox".
Yes, that's correct.
Here is my usage sequence on my Android mobile, once I have launched the album:
1) Select one image folder.
2) The slide show start automatically (by passing the "turntable" animation").
3) The display is not
in full screen (although display is set for that, thus truncated) and the slide show runs. See screenshot posted above.
4) Press e.g. the left arrow: the slide show stops and the left menu is displayed again.
5) Press the "Start slide show" button and everything is fine i.e. it is in full screen mode.
So to me, as the full screen is not supposed to be set automatically, it looks like there is some conflict in the "Projector" settings between the "Open in Full screen" checkbox and the "Automatic start" checkbox".