Just saw this feature listed in the 'Early Access' :
DHCPv6 and IPv6 RA Guard
Enables DHCPv6 and RA Guard for IPv6.
Opt-in settings
Requires MS 16 or higher. This feature is applicable to the following models:
MS120, MS125
MS210, MS225, MS250
MS350, MS355
MS410, MS425, MS450
Is MS16 in a private beta ?
Not that I care about ipv6, but just curious that open beta features are requiring a firmware that is not publicly available yet