This is different, it worked for netinstall, but continued to only boot to ethernet after netinstalling with no fallback to nand. This is also present in ROS 6.47.10 as well as being available in the current v7.1RC4 release. I don’t think this option is related to http://forum.mikrotik.com/t/please-mikrotik-made-netinstall-version-for-docker/151803/1
HIding the MAC address it’s useless, it’s silly, just a machine directly connected to the router “might” be a problem,
but with serial number can be deducible the address of the cloud lowercaseserialnumber.sn.mynetname.net
and if the routeros use the cloud, everyone in the world can have your real IP address,
and sometime can be a problem…
But going back to “ethernet”, only the latest RouterBOOT 6.45.x and up on selected device models can have the possibility to select ethernet,
instead RouterOS really do not count, just must have the internal support to set that option.