So I looked around and it seems like there is no Org level call that will provide that information. I was able to get it working but its inefficient because it needs to query data from every client at every network as it seems like "getNetworkClientPolicy" is the only way to grab that info.
import meraki, json
org_id = ''
api_key = ''
mapi = meraki.DashboardAPI(api_key=api_key)
networks = mapi.organizations.getOrganizationNetworks(organizationId=org_id,total_pages='all')
allow_clients = []
for network in networks:
clients = mapi.networks.getNetworkClients(networkId=network.get('id'))
for client in clients:
data = mapi.networks.getNetworkClientPolicy(networkId=network.get('id'),clientId=client.get('id'))
if "Whitelisted" in data.get("devicePolicy"):
allow_clients.append(client)
break
print(json.dumps(allow_clients,indent=4))
That code will provide a list of client dicts (allow_clients) with the manually set "Allow list" / "Whitelist" attribute.