Consultant for well over a decade now. I've worked with quite a few MBB kids over the years as well as with clients who previously hired them. I'd say it's fairly uncommon for clients to actually yell at the analysts on the ground, but it does happen. It's more likely that the MBB associate or engagement manager gets yelled at for various reasons. But it's a lot more common for the analysts to be told "do whatever the client wants" and end up working absolutely stupid hours to cover client demands that should have been pushed back on, on top of internal commitments to stay on the right side of the "up or out" funnel.