It may have made sense in the pre-Level-C SIM era, completely get that. In today's world of CAT II/III from day one, mandatory FDs and an equal share of handling between LH/RH, it lacks practical meaning.
If I see any effect at all, it makes the handling and decision making part of PIC job more complex on a particular day. Exactly the opposite from "newbie safe space" the rule was (most likely) hoping to create.