Windows 8.1

I'm finally trying to get me head around ipv6

I was somewhat alarmed to discover that the low order 64 bits are
reserved for what someone called 'hardware addressing schemes' but I
can't remember where I read this.

https://en.wikipedia.org/wiki/IPv6

"In IPv6 when using address auto-configuration, the Interface Identifier
(MAC address) of an interface port is used to make its public IP address
unique, exposing the type of hardware used and providing a unique handle
for a user's online activity"

The article then goes on about 'privacy extensions'

"Privacy extensions are enabled by default in Windows (since XP SP1), OS
X (since 10.7), and iOS (since version 4.3). Some Linux distributions
have enabled privacy extensions as well"

If I open a command window I get

Physical Address. . . . . . . . . : 6C-FA-A7-3A-45-AC
....
DHCPv6 Client DUID. . . . . . . . :
00-01-00-01-1C-E1-07-B6-6C-FA-A7-3A-45-AC

and can see the physical address on the end of the DUID.

The local library recently demanded the wireless interface MAC addresses
from our local user groups laptops saying it would 'make our lives
easier as we no longer had to log in to the wireless network' but I
suspect it has more to do with tracking our usage.

Am I right to be concerned?

Thanks

--
Quis custodiet ipsos custodes?
Who watches the watchers? (loose translation)