Not being able to apply a policy between interfaces of the same zone is inconvenient.
Even cisco in the 15.x series now allows this, because it's really useful. Else you end up often having to define 1 zone per interface ...
Imagine the case (which I think is pretty common) of N LAN segments that should be completely isolated from each other but be able to access the internet.
Ideally I'd create a LAN zone and a WAN zone, and set the intra policy of LAN to DROP.
Instead I have to create N different zones, each time with the same policies applied to them.
When in addition to the WAN zone you have a 'service' zone with shared internal services, this gets even worse.
If the "from SAME_ZONE" doesn't exist, behavior shouldn't change and stay accept. But if it does, then apply the policy. It could either follow the same syntax as from XX { firewall ... }. Or be something more explicit to note the difference.