I'm not sure if this is just a misunderstanding on my part, in the following picture I expected both Ornithopters to be hit when my dwarf warrior played Weak Chop. It looks like "Whizzer", the one on the right (I think), wasn't targetted. The next time I played weak chop and the golem was in range, I both enemies were targetted. Is there a mechanic I misunderstood? I thought perhaps it might be the case that I was allowed to specify only one target, but the second time both targets were automatically chosen.
That looks like a facing issue, you don't seem to be able to chop both of the onrinthopters the way Shorty is standing; one is in front of you, the other behind. If the Golem moves into the square next to Ezzard, you will have both of them in the same zone, i.e. in front of you and so the chop will hit both.
Interesting, mentally I was treating it as two separate attacks that I could aim wherever required. Your explanation makes sense, so it's probably working as intended (effectively 5 squares of valid targetting area).