Looking back through the Chimpanzee Genome Consortium (2005) paper, I find this:
Chimpanzee polymorphisms. The draft sequence of the chimpanzee genome also facilitates genome-wide studies of genetic diversity among chimpanzees, extending recent work. We sequenced and analysed sequence reads from the primary donor, four other West African and three central African chimpanzees (Pan troglodytes troglodytes) to discover polymorphic positions within and between these individuals.
A total of 1.66 million high-quality single-nucleotide polymorphisms (SNPs) were identified, of which 1.01 million are heterozygous within the primary donor, Clint. Heterozygosity rates were estimated to be 9.5 x 10-4 for Clint, 8.0 x 10-4 among West African chimpanzees and 17.6 x 10-4 among central African chimpanzees, with the variation between West and central African chimpanzees being 19.0 x 10-4. The diversity in West African chimpanzees is similar to that seen for human populations, whearas the level for central African chimpanzees is roughly twice as high.
The observed heterozygosity in Clint is broadly consistent with West African origin, although there are a small number of regions of distinctly higher heterozygosity. These may reflect a small amount of central African ancestry, but more likely reflect undetected regions of segmental duplications present only in chimpanzees (Chimpanzee Genome Consortium 2005:70, emphasis added).
I included the context before the "broadly consistent" to be clear about what it refers to. Elsewhere in the article, the consortium identifies "Clint" as a "captive-born descendant of chimpanzees from the West Africa [sic] subspecies Pan troglodytes verus" (CGS 2005:70). So Clint's heterozygosity isn't just broadly consistent with West African origin; it is an example of West African origin.
Now, the "broadly consistent" is there because the overall heterozygosity estimate for Clint is a bit higher than typical for West African chimps. So why don't they just say that? It's not like Clint's origin is a mystery.
And there are plenty of good hypotheses for why one captive-born chimpanzee might have slightly higher overall heterozygosity than other members of his subspecies. The paper lists two; others include the possibility that Clint's captive ancestors were taken from different parts of West Africa, or that the captive breeding program avoided inbreeding more than wild chimpanzees. Any of these might be tested; they weren't, so we're left with the "broadly consistent" answer.