In fairness, is the arrow really any different than marking parallel jacks on speakers, "in" and "out" as I have seen many times from different manufacturers?
An "in" and "out" 1/4" jack on passive speakers could be two different current handling jacks. Since the input is carrying 2x the current as the output jack. At Peavey we had a dual-tip contact high current 1/4" jack and then normal single tip jacks. I could hypothetically imagine using a high current jack for the input side and lower current on the output side, while I concede this is a stretch. I'd use the high current jack for both.
Another subtle difference inside the loudspeaker there is a wire or PCB trace between the two jacks, and then the speaker connects to one jack or the other. Labeling one jack the input, and connecting the internal speaker load to that jack, reduces the current flowing in the wire link feeding the output jack.
So there can be actual differences. It will still work if you plug it up backwards, but the internal link wire is carrying 2x the current.