Filigree isn’t just Nightborne as it’s regularly part of Night Elf jewelry/armor. Filigree would address Shen’dralar + Kaldorei themes pretty easily. It filled both themes for Night Elves.
In no way is filigree just Nightborne. zero
It would be like saying a circlet is just Draenei and no other races can wear one with a jewel in the center.
I’m having a hard time understanding you.