Totally disagree with that.
Mckinsey Implementation is still below the McKinsey brand, which is what counts here.
It´s just a more especialized branch that has always existed and has always had demand, but now fully branded, with a name, etc.
Exit opportunities are influenced by (1) the power of the brand and (2) your specific footprint in the firm -types of engagements, industries, clients, etc-. Hence, it only affects the 2nd.
Hope it helps!