Their whole relationship was about dissolving the boundaries between lover and beloved. Scholars actually say it’s impossible to tell in a lot of Rumi’s poetry whether he’s addressing Shams the person or the Divine. In Sufi tradition, ‘lover’ means lover of God specifically. So when he writes about love it operates on both levels simultaneously - human connection and divine connection are the same thing.
Rumi described love as a force that ‘makes the seas boil, crushes mountains into sand.’ Something that transforms everything it touches. And relevant to what you’re saying about not holding on, he wrote that the Beloved is living while the lover is dead. It’s about letting go of the separate self.
After Shams disappeared, Rumi didn’t just grieve. He wrote an entire collection of over 40,000 lines called the Divan-i Shams dedicated to him. He wrote as if he and Shams were the same person. Some people talk about the idea of inner union, and for some, it’s a step before reaching a physical union with their TF, but others believe it is their final destination.
Personally I think this idea of “inner union” is just the end stages of your surrender stage and that’s why we have so many people gatekeeping the TF community because they can’t get beyond that stage so they start telling other people that they can’t possibly reach a physical union with their twin either.
I don’t think one is better than the other… I think maybe Rumi was a twin flame but it doesn’t mean other twins can’t be in physical union.