Absolutely NOT true, never has been true that I'm aware of... please don't make such claims until you know what are you are talking about
Windows OS Ethernet Network Interfaces not explicitly tagged as Private will default to Public (as it should. The only users caught up by this are those ... delete rant about PEBKAC ).
More specifically in this context, networks defined as "Unidentified network" are considered public by default. One prerequisite is that the connection's TCP/IP protocol stack settings must have its "default gateway" setting configured. The other is that said Gateway has some ability to get to the Internet, whether directly by actually having an Internet connection, or indirectly through another upstream router.
I think the test is that if it can reach a specific Microsoft-controlled address, then the system will ask for the type of network to consider the connection as being part of.
And every Windows OS I've used (with this nomenclature) has prompted when a new network is connected to an Ethernet interface. Which means.... the issue was not properly configuring the network interfaces for the environment/network, and/or assuming incorrect things
From what I can tell, only network configurations that can actually reach the Internet will receive a prompt asking about the type of network the network connection in question is presently on. If it cannot reach the Internet, the prompt will never come, so the network is flagged as an "Unidentified" one.
Given an "Unidentified" network, you now have to figure out how to set the connection to "private" if the need arises, e.g. point-to-point connections or ad-hoc networks that don't need an Internet connection. In fact, the Metro/Modern/Universal/Whatever-it's-called-today "Settings" interface won't even let you create such a connection. N
etwork connections configured using the aforementioned "Settings" app must have a "default route". Instead, you must use something else, like the "Control Panel" method, whether directly (via the "ncpa.cpl" Control Panel applet) or via the Network and Sharing Center/Change Adapter Settings method.
--Katt. =^.^=