The article doesn't really comment on the merits of the case for Kirtsaeng. The EFF isn't trying to convince people to support any position in that case, nor should they, I agree with you that it is definitely a legal grey area.

What the EFF is taking issue with in that case is the potential precedent that could be set depending how the case turns out that could undermine first sale. The only reason EFF is interested in the case is because the legal arguments being used could impact first sale.

What's happening in that case is not simply that publishers are trying to claw back rights from US consumers

True... but that's the part of the case that the EFF is concerned about.

In contrast, in the Capitol case the article very clearly takes a position, and while I'm not familiar with that case I give the EFF the benefit of the doubt and assume they're being truthful.