No, I use fly proxy all the time and also only have the Hobby plan.
(I’m 99% sure that the personal up there is meant solely as a disambiguating organization ID—and not as a billing class.)
As a temporary workaround, it is always possible to bypass DNS and provide a numeric IP on the fly proxy command line:
fly m list -a <db-app-name> # consult the IP ADDRESS column
fly proxy 5432 fdaa:<hex-digits-from-above>:2