are certainly related; the only question is whether they are (necessarily)
There are two distinct controversies about the use of lexicostatistical
methods. One issue is whether the family trees produced for languages
with fairly high cognate percentages (say 60% and higher) are a reliable
indication of the detailed structure of "genetic" relationships
among languages. Everyone accepts that two languages with 85% cognates
are certainly related; the only question is whether they are (necessarily)
"more closely related" in a historical sense than either is
to a language whose cognate percentages with both are (say) 80%.