Different McKinsey teams were hired by different entities to do different things.
To the extent that those teams are not related or coordinating, that's understandable and not a breach of ethics.
An Accenture division can be helping to the IRS build tax compliance software while another division help companies write tax minimization software.
There are only a small number of 'Big Accounting' firms, and they all have overlapping interests.
Banks to similarly.
McKinsey, Goldman, Accenture, all the big accounting firms are always working with 'Big Pharma' and 'Government' at the same time and all of the parties know this.
While we do need to be wary and cautious about backchannel information passing etc. - the notion that there's a breach of public interest as it is being presented is hyperbole.