It is odd, as you say, but I don’t think it’s particularly sinister – just a bit unnecessary. Logically, if people vote against ending the dispute, then they are voting to continue it – or am I missing something here?
As far a submitting a motion that is directly contrary to another one that’s been submitted by someone else, again there’s no reason why they can’t but I can’t see why you would ask people to vote twice on the same issue.
If I were chairing this meeting, I’d call for a vote on the first motion then rule the second one ‘out of order’ since the decision had already been effectively made.
The only difference might be if the contrary motion included a qualifying paragraph. For instance, it could be a) stop the legal action or b) continue the legal action up to a limit of a certain amount or money or until a specific stage or something like that.
But if you are voting yes or no, you don’t have to vote no to no, then yes to yes. One vote suffices.
Perhaps the secretary just wants the owners to be aware of the choices – but you’re right, it’s a weird way of going about it.