The concern about cross-posting is understandable. And if someone grants 200K SP, I'd say they have the right to stipulate certain requirements re the use of that SP.

But as you point out, the requirements are not very strict. It states "particularly those that are not cross-posted on other platforms"

I believe we can take that to mean that you would focus on those that are posted solely on Steemit. But that if you upvote certain posts that happen to be cross-posted on other platforms, there will not necessarily be any negative ramifications.