A sure sign that I've read way too much yuri drama was that I was genuinely surprised that they stuck together after high school. I was really expecting the relationship not to last like most yuri manga where they get separated after graduation.
It felt very purposeful in taking a lot of yuri tropes and undercutting them one by one with a specifically lesbian take.
She talks about previous same-sex crushes from a young age, and identifies herself as one of "them", instead of their romance being that standard yuri first crush where she learns about feelings in a safe penis-free space and then they graduate on to heterosexual dating.
People know she dated a girl before, and they connect that to her being gay, not just some sort of yuri schoolgirl thing not to be taken seriously. Being identified as a lesbian is something that complicates her relationship with others.
Ending specifically by saying yo, this is a real relationship that lasted, not just some schoolgirl stage. And communicating that to a younger generation of girl who herself is wondering if her own same-sex experiences are "real" or not.