We were looking for the Voze mansion and having trouble finding an exterior and interior to match, as most wealthy estate-type people heavily renovate their interiors and look more McMansion inside. The exterior was a house in Pasadena.
I think this is saying that they had a problem finding a home fit for wealthy characters because the homes with the gravitas-invoking exterior did not necessarily have the same kind of interior. Having lots of money can be associated with a particular aesthetic. Describing a portion of the home as having a McMansion look is not usually a good thing. It is a negative term. I imagine a McMansion interior could involve the latest trends, having large spaces, and going for shock and awe rather than refined details.
Through the magic of filming and editing, a different exterior and interior can be put together without too much evidence otherwise. Of course, it is also fun to watch for situations where they do not exactly match.