I’ve heard this kind of suggestion in regards to other invalid weddings (e.g., a Catholic marrying outside the Church or a remarriage after a divorce) and I don’t understand the thinking.
You won’t attend the wedding because you don’t approve. But you’ll go to the reception and celebrate the wedding.
Why would you celebrate something that you think is wrong?
It seems more consistent to either attend both the wedding and the reception because you love the participants or hope to nurture your relationship with them so that eventually you can lead them back toward Catholic teaching. Or else skip both the wedding and the reception because you want to show your disapproval.
Maybe there’s something I’m missing in this solution.