[ghshephard]

In these contexts - neither of the addresses was intended for internet consumption. A misconfigured firewall exposes you in the case of IPv6 routable addresses, and is less relevant in the case of IPv4; the ULA IPv6 address is roughly the same as an RFC 1918 address with it's lack of routing on the Internet.

The point I was (poorly) trying to make is that non-routability is sometimes an explicit design objective (See NERC-CIP guidance for whether you should route control traffic outside of substations), and that there is some consideration that should be made when deciding whether to use globally routable IPv6 addresses.