Same here, the SRX in 10.2R2 doesn't respond to ICMP6 router solicitations:
15:42:24.655114 IP6 :: > ff02::1:ffb4:48c2: ICMP6, neighbor solicitation, who has fe80::223:32ff:feb4:48c2, length 24
15:42:25.695227 IP6 fe80::223:32ff:feb4:48c2 > ff02::2: ICMP6, router solicitation, length 16
15:42:26.695368 IP6 fe80::223:32ff:feb4:48c2 > ff02::2: ICMP6, router solicitation, length 16
15:42:28.695625 IP6 fe80::223:32ff:feb4:48c2 > ff02::2: ICMP6, router solicitation, length 16
15:42:32.695681 IP6 fe80::223:32ff:feb4:48c2 > ff02::2: ICMP6, router solicitation, length 16
15:42:40.695669 IP6 fe80::223:32ff:feb4:48c2 > ff02::2: ICMP6, router solicitation, length 16
15:42:48.695793 IP6 fe80::223:32ff:feb4:48c2 > ff02::2: ICMP6, router solicitation, length 16
15:42:56.695832 IP6 fe80::223:32ff:feb4:48c2 > ff02::2: ICMP6, router solicitation, length 16
jeje@gw1-1.tip# show protocols router-advertisement
interface reth0.134 {
managed-configuration;
other-stateful-configuration;
prefix xxx:xxx:8100:1::/64;
}