Policy of Communist party of Yugoslavia until 1948 was Marxist-Leninist, same as policy of All-Union Communist Party(bolsheviks) until 1956 namely Stalinist. Yugoslavia after revolution and victory in People's Liberation War has been one of the most "ortodoxs" communist countrys in the world. Yugoslavia copied Stalinist policy of Five year plans and collectivization... Soviet military and industrial advissors and missions were sent all over Yugoslavia to help in socialist reconstruction of country...
The Paradox developers who came up with the Hearts of Iron policy sliders didn't base them on analysis of political economy, they are based on fuzzy liberal conceptions of freedom vs totalitarianism. According to their worldview, Tito was not "Stalinist" because he didn't forbid emigration and open death camps for dissenters. That's all there is to it. Notice it takes less slider moves to shift from Fascism to Leninism than from Fascism to market liberalism.