I might be talking about Bain only, but having a case exclusively focused on market sizing at Bain is extremely unlikely. When we "create" our cases, we have clear guidelines, and market-sizing only cases don't give us a chance to evaluate candidates across all dimensions.
This being said, you can definitely have a market sizing "sub-question" in a P&L or revenue growth case for instance, and I would guess this happens in 10-15% of the time, and certain offices may be more likely to give market sizing than others.
I have also heard that BCG (at least in London) is trying to tweak the format of the first rounds and include necessarily a market sizing there - not sure if this is systematic and if this is the case in other offices.
I haven't heard that McK are necessarily big fans of market sizing, and I expect an approach similar to Bain, you may need to size a market but that would be part of a broader question - again to be verified for the office you're targetting.
Overall, I'd say the best way to know this would be to ask a few consultants from the office you're interested in at MBB and compare their answers.
I hope this helps! :)