Ah ok. So this is about the composition of just the star and not anything about the broader system.
Consider that our sun contains 99.86% of the mass of our Solar System.
Bear in mind the headline is about total spectrum of elements in entire galaxies ... eg: as in looking at our galaxy, the entire milky way, from a distance that makes it dwindle to a near point and difficult to estimate how many stars make it up.
Of all the many galaxies that we can see, this is a story about a handful that are mostly hydrogen and helium .. more so than what we see as typical for galaxies.
Consider that our sun contains 99.86% of the mass of our Solar System.
If you dumped that into a Sun-sized metal-poor star, it would probably pass for metal-rich.
A Sun sized metal poor star wouldn't be surrounded by large amounts of orbiting heavy elements .. that would suggest even larger amounts failed to orbit and fell into that star.
( I'll freely confess to being decades out of date on the conjectured life of stars though, these days I mainly do geophysics related to astrophysics (cancelling out ground effects from SKA type projects) )
But as the black hole approached, Hieronymus noted there was no gravitational effect. He studied it more closely and announced, with a chuckle, that it was not a black hole after all.
“It’s nothing,” he said. “Just an ordinary asteroid someone has painted black.”
https://www.space.com/31456-rocky-planet-found-unlikely-star...