Email notification for unknown sign-ins and ipv6

Hello,
I’m a bit annoyed by the frequency of these “sign-in from new location” emails. In my case I get them because my IPv6 address changes regularly (RFC4941). However the IPv6 prefix stays constant, so I wonder if the process checking the currently used IP against the list of already used IP should (for IPv6) only compare the first 64 bits instead of the whole address.
Best regards
ukleinek