Exactly--and priests can affirm that a same-sex couple is not in mortal sin due to mitigating factors, and that their relationship is not a scandal to the congregation, since the congregation welcomes the couple. And this is all basic Catholic 101--even before Amoris Laetitia. Objective sin does not equal mortal sin. 

I would bet there are sins you commit every day which would normally be mortal but for which you know there are mitigating factors--I know I sin. And I know that God frequently does not hold me culpable for reasons which I know in my conscience by the Holy Spirit.