Seems like you have to first disable the active store and then the persistent store.
This worked for me and have worked accross multiple reboots.
netsh interface ipv6 set global randomizeidentifiers=disabled store=active
netsh interface ipv6 set privacy state=disabled store=active
netsh interface ipv6 set global randomizeidentifiers=disabled store=persistent
netsh interface ipv6 set privacy state=disabled store=persistent
netsh interface teredo set state disabled
Also, if you have a static IP configured and want to disable SLAAC:
netsh interface ipv6 set interface "Lanesskog" routerdiscovery=disabled store=active
netsh interface ipv6 set interface "Lanesskog" routerdiscovery=disabled store=persistent