Recently, looking under the hood of a 70s era car, I noticed the radiator fan and the little fan on the alternator are not regular and symmetrical, but a bit lopsided.
Wouldn’t this give an irregular cooling effect?
Not really, the average airflow through the radiator determines cooling. An irregularity of tiny fractions of a second between fan blades will make no difference. AFAIK the fans are made that way tgo avoid harmonic vibrations but someone might correct me.