Comment 19 for bug 1764853

Yes, I think a version between 16.04 and 18.04 added this (Don't remember what version).

If someone installs libnss-resolve it will modify nsswitch automatically.

I think we can close this ticket since it does not apply to a default configuration.
Also I think /etc/hosts is not empty by default but still contains localhost and hostname.
Just keep in mind that myhostname would also allow removing localhost and hostname from /etc/hosts. I expect ubuntu to do that at some point in the future.
In that case installing libnss-resolve could make problems that are not easy to track.