A large number of publications have shown suprisingly accurate predictions of which species are susceptible to SARS-CoV-2 infection using just the variation in ACE2 proteins found in different species. This would seem to imply that receptor-binding is the primary barrier to cross-species transmission for this virus. However, we show that the predictive power of ACE2-based models derives from strong correlations with host phylogeny rather than processes which can be mechanistically linked to infection biology. Further, biased availability of ACE2 sequences leads to misleading projections of the number and geographic distribution of at-risk species. Models based on host phylogeny reduce this bias, but identify a very large number of susceptible species, implying that model predictions must be combined with local knowledge of exposure risk to practically guide surveillance.