I know this guy and he isn’t a liar. - minimus
Probably more a matter of perspective.
I suspect there is are at least a few people who first become interested from obtaining literature from a cart, who move forward to studying or becoming full JWs. If the carts didn't have any success, then why keep doing it? It would be an un-motivator if JWs attending the carts never see anything positive for their efforts.
Other causes for congregation attendance growth include locations which offer benefits such as nearby jobs, new development, ease of transportation, reasonable living costs or activities for retirees, thereby causing outsiders to relocate there including JWs from other areas.