One thing that is unusual about the star relative to our regular experience is how little “metals” it contains (in astrophysics metals are any elements heavier

One thing that is unusual about the star relative to our regular experience is how little “metals” it contains (in astrophysics metals are any elements heavier than helium). Metals heavier than iron are only created in supernovae, lighter metals still only get created in stars. Either way, if it was created a few 1e8 years after Big Bang, there weren’t many of those going around. Now, most of our models for stellar evolution are calibrated to stars we see, which have plenty of metals in them. Whereas this one doesn’t so our models could be off.