Yes you are right. But be aware, that as soon as you activate IPVv6 on WAN settings, you expose all your clients behind the Peplink router to the WAN. So better have a e.g. a Fritz!Box with IPv6 firewall (at least deny all inbound rule) before the router.
See: Post
Has this behavior changed in firmware 8.6.0 RC4? Does the B One now provide a stateful IPv6 firewall for routed traffic, or does it still rely entirely on the upstream router’s IPv6 firewall?
For me it would be helpful, if the PL router could create a /62 or /64 IPv6 network for every VLAN based on a /56 IPv6 network received by Prefix Delegation from the provider router.