Umm blood elves very much consider themselves Highborne because they are. Up until the Scourge invasion, they were led by Anasterian, a first generation Highborne like Thalyssra and Azshara. Show me your source where blood elves have said they don’t consider themselves Highborne. Even void elves are aware that they’re Highborne and still hope for a reunification with their sindorei relatives. They want it to happen via them joining the alliance so they’ll never get their wish but there fully aware of who they are and where they come from.