In terms critique the phrasing of a statment, I too am not understanding the difference between them. I haven't spotted an example of pleonasm that did not look like a tautology and vice versa. 😅

To answer your first question left communism is neither of these. It is a specific set of tendencies within communism characterised with adherence to idelogical purity. Left communists deride all socialist and communist experiements that have existed because according to them these efforts did not practise Marxism properly. They do not like pragmatism.