Help me visually understand routing

In your diagram the “VLAN interface” box should be outside of the bridge, and the bridge interface is where the L3 VLAN interfaces meet the bridge – not inside it. But it more like a Venn diagram: check out the “RouterOS bridge mysteries explained”: http://forum.mikrotik.com/t/routeros-bridge-mysteries-explained/147832/1

Basically the VLAN table in the bridge is essentially the allow/deny at the L2 layer, which is entirely separate from VLAN interfaces that are L3 constructs.