It was once popular. I recall reading about it once, it was labelled the kangaroo jump layout or something like that. It's purpose is something to do with staggering the baffle responses.. I don't recall it being anything too exact, but randomising diffraction isn't an exact thing. Apart from that you'll find lobing works on that angle. It's anyone's guess whether that was a consideration but it's interesting to wonder what that might do to bring consistency to sides vs ceiling reflections.
Whichever way, if the drivers are not centred on the baffle, one should have mirror imahed loudspeakers.
dave
dave