So from the wiki

The monophyly of Xenacoelomorpha soon became established, but its position as either a basal bilaterian clade or a deuterostome remained unresolved until 2016, when two new studies, with increased gene and taxon sampling, again placed Xenoturbella as the sister group of Acoelomorpha within Xenacoelomorpha, and placed Xenacoelomorpha as sister to Nephrozoa (Protostomia plus Deuterostomia), and therefore the basalmost bilaterian phylum<

Seems like “where on the tree of life” is “the first bilaterals” which makes sense. They seem very worm-like in bodyplan. Shit from the Pre-Cambrian can look pretty alien and have shaky relationships to more derived species.