As long as work demands that you engage with who you are, work transforms you. If work does not impact who you are, then work does not transform you.
For example, if you have power and power is part of who you are, then any work where you have to modify your relationship with power will transform you.
Similarly, evolution through knowledge work can only take place if, inside you, there is an ego/ identity of knowledge, and this identity is being called into question in some way in the course of your work.
In short, you evolve through work because of your identity and the struggle of your identity with the work.
Identity with the work makes you strive for excellence. Yet to grow and evolve, one has to transmute that very identity. That is the paradox of “identity with work”.