His transparent attempt to incrementally legitimize relationships based upon mortal sin by claiming that such arrangements possess an incidental good is a contradiction of Catholic moral teaching. He is, in essence, proposing that an evil tree can bring forth good fruit. Suppose he made the same positive claims regarding adulterous relationships? Don't adulterous couples also share "luv" and friendship and so forth? How about gluttons? Eating sustains life, after all, so food might also be characterized as a "precious support in the life of the glutton", right?
Only a corrupt perspective would lead someone to claim that elements of goodness exist in the midst of that which is fundamentally evil.
The idea would not be to uphold or relativize contraception, which is a gravely sinful practice, but to recognize that their life together consists of more than the perversion of sex.
Nevertheless (in agreement, I think, with you), I would not want any such venture to "find the good" in these defective relationships, in a Vatican document. It's the kind of thing you could explain in a novel, but it will be exploited as a sentimental pat-on-the-head "attaboy" if it's put into a teaching document.