If there is strong evidence that some phenomena cannot occur (e.g., that there's an inherent barrier to deer-to-deer or deer-to-human transmission), then any further human risk is slight. If however there's merely a lack of evidence of various forms of transmission, then we can't be assured that there is no such transmission. (This was the case with airborne-transmission of COVID-19, early in the pandemic, where "no evidence" was broadly interpreted as "not possible", incorrectly as it turned out.)
I'll also note that the lack of symptomatic illness among deer does not mean that the virus doesn't spread and propagate within and from the deer population.
