IPv4 entries should not appear when Dualstack VM subnet associated with Router where subnet belongs to IPv6

IPv4 entries should not appear when Dualstack VM subnet associated with Router where subnet belongs to IPv6.

1. Create N1 and S1(IPv4) and S2I(Pv6)
2. Create Router and Associate only Subnet2 (IPv6)
3. Verify FIB entries.

Expectation:

       Since, I am adding IPv6 subnet, I am expecting only IPv6 entries should come to FIB.

Observation:

       Both IPv4 and IPv6 address observed in FIB.

      Please let me know whether this is valid scenario.