That's a reasonable argument. But it requires a very high level of understanding of (bat) corona-viruses in general with a majority of corona-viruses that exist having been sequenced etc.

From my (limited) understanding we only know about a fraction of corona-viruses out there, and hence there is great uncertainty in the phylogenetic modelling.

I haven't seen a credible write-up, if you can point me in the right direction, that would be appreciated.