i was just reading an article on 4T bench flow testing.
scroll to swirl and tumble,
in essence: "Within the industry, a debate has been raging on mixture motion with some looking to increase it, while others want to eliminate it."
what i walked away with was:
"the energy that's used to swirl the mixture would be best used to increase the airflow capacity"
you do not want the intake charge mixing with the exhaust inside the cylinder, don't cross the streams.
tumble perfectly describes loop scavenging.