If you are referring to L3/L4 firewall logging it will actually mention it in each line.
So if you enable a syslog server on your network and point the Meraki network to it, you can choose to add the "flow" logs. Then each firewall rule will have a box to enable or disable logging for that specific rule.
These will be included.
But what about group policies?
They are logged by default and the syslog message will actually say: allowed due to group policy.
It will however not mention what rule it matches though.