At least at McK and BCG it is quite difficult to move from a research position to a pure consultant position. I helped a person recently that after working at McK in the research division had to do an MBA to be able to move to a pure consulting role.
It is not impossible to do the transition, but it is definitely better to start in a pure consulting role from the beginning.
Here's a recent thread on the same topic: https://www.preplounge.com/en/consulting-forum/from-associate-bain-capability-network-to-consulting-position-possible-9060
It's possible but you should plan the transition effectively.
It's possible and I've seen people do it, but typically though an MBA in between.
Here's a recent post on this with more detail:
I have never seen it happen in the time that I was in McKinsey, but honestly, this does not mean anything, I am sure there are cases.
Something that would help for sure is an education break in between. Business school is very common for people who are thinking of switching carreers.
Hope it helps!
What's your actual question?
as pointed out by others, I agree, it's not impossible, but it is better if you do an MBA in between.