So you have to think of this in two directions.
UPLINK - Traffic from your client to the AP
DOWNLINK - Traffic from your AP to your client
Downlink is where Meraki can apply QoS, so destination port is accurate in this case.
Uplink is 100% controlled by the client side, so there is nothing Meraki can do in this case. If the client is sending traffic correctly marked with the QoS value your looking for then your good to go by default on that front.