I would asset that simply because the phrase “guarantee access” has been mis-used by ilinformed politicians doesn’t necessarily mean the Pope uses the phrase incorrectly.
I guess that’s all I can say on the matter if you aren’t willing to consider the possibility that mis-use of the term in the past doesn’t mean it can’t be used correctly in the present.
Taken with all the other statements the Pope made on economics in his statement, I have no alternative but to infer that the Pope uses the phrase in exactly the same way as the socialists.