The answer to your question, "...then are both considered lead link or should one be assigned a 'focus' of lead link?" is, they are BOTH considered Lead Link.
Avoiding the issue of why it's bad to do this, I can at least say that it is definitely NOT that one of them would have a "focus" of Lead Link, because every role-filler is accountable for ALL of the accountabilities of that role. The focus just specifies some further distinction of application or context to maintain clarity. I want to clear up [@mention:523162737680436711]'s point, "Important in that case is that it is absolutely clear which Focus is doing which Accountability" because that seems to be based on a misunderstanding. If you're in the role, you're accountable for each accountability of that role.
Given that, 2.4.2 hopefully makes more sense.