I’m always wary when I hear EY practitioners quoting research, especially statements that begin "all the research shows......"
The first thing to remember: EY training on such research is about theories . Unfortunately the sector seems in an altogether undignified haste to treat theory as if it were fact.
This tendency is exacerbated by training and "education" programmes which are based on a tick-box approach, whereby the student receives a qualification in return for delivering "correct" answers to a set of criteria. Any attempt by the student to question, challenge, criticise these "correct" answers is severely discouraged by the simple expedient of returning a "criteria not met" response.
Some of these theories and some of the research that claim to support them are valuable within certain situations and parameters. But in many cases, the applicability of a theory is over-extended beyond any supporting evidence.
Much of the research is downright bad, such that it would not pass muster if presented for the first time today (looking at you, J Piaget.) Some research is contradictory, and opposing research is commonly manipulated in and out of fashion over time by policy makers to meet current social needs (attachment theory being a much kicked-about socio-political football.)
Most research suffers from being applied to childcare/education in a cynical 'pick and mix' fashion. Virtually all of it is presented to EY practitioners in a very superficial manner which devalues whatever worth it might have if they were ever encouraged to study it properly.