Earlier quoted context omitted.
Helots were 85% of the population[1]. GP is pointing out that random skeletons don't come with residency papers describing which kind of residents they belong to. [1] Source: https://acoup.blog/2019/08/16/collections-this-isnt-sparta-p...
"Sparta" is commonly understood to mean the city of Sparta as a political entity and "Spartans" its free inhabitants. Only in the blog you quote is the term "Sparta" used to refer to the wider city-state of Sparta that encompassed subjugated settlements outside of Sparta. Historical sources, ancient as well as modern, do not consider the helots to be "Spartan" (or even "Spartiate", a term made up by the author of the…
I would suggest reading the posted blog-post. The author do know what he is talking about and–in my opinion—quiet an engaging writer.