debugonce(table.integer64)          # set a stopping point
invisible(table(as.integer64(1:3))) # not hit

Other integer64 implementations rely on S3 generics being put in place by {bit64} itself, e.g.

Currently the user has to call table.integer64() directly to access this code. I don't see anyone having done so:

https://github.com/search?q=lang%3AR+%2F%5B%5E%7B%5Cw.%5Dtable%5B.%5Dinteger64%2F+-path%3Ahighlevel64+-path%3A.rd&type=code

It would be nice for table(x) to "just work" for users to get this custom-tailored implementation.