That hardcodes the source layout? I don't buy that a tool that's being sold for money would do that (precisely because there's no standardization in the C++ world; any tool that wants to have more than 1 customer will have to support more than 1 directory layout), and if the tools are internal then by definition you have the ability to make changes to them.
> Fundamentally: the codebase has worked perfectly well this way for the last 20 years; what's the business case for changing it (at potentially significant cost) just to be compatible with XYZ new tool that everyone is rallying behind?
Well, if you make adopting good tooling in C++ harder than switching to a language that already has good tooling, don't be surprised when developers do that.