I was very upset when I read this at first. But I’ve seen the later clarifications by Vatican people and it seems to me the pope did not discuss any sort of recognition of gay sexual relationships be it civil unions or marriage. My understanding is that he was asked about his comments from before in Argentina and he tried to explain what the rationale was at the time the gay marriage debate was ongoing.
I do not see how ANY catholic case could be made to give any sort of public legitimacy to relationships deemed inherently wrong. Even if you call it a civil union, it’d be wrong.