I think many lawyers, and firms, regularly use the term "Corporate" to also include commercial transactional work rather than only M&A, JVs, structuring and restructuring etc. It's common, for example, for tech transactional partners to sit within a firm's Corporate group.
But I fully agree that very many of the practice areas within City firms involve very little black letter law, the exceptions being areas such as Tax and Litigation. Even major complex litigation may not involve points of contention on the law, but be focused on disputes on the facts.
That doesn't mean that the lawyers at those firms aren't very good at what they do: managing a multi-jurisdictional complex merger, or vast project financing, with multiple parties is a huge undertaking but they're rarely reaching for their copy of Chitty. There's an apocryphal story of a lawyer giving a eulogy at a highly-regarded partner's funeral "Keith was the best lawyer I ever met, it's just a shame that he could have written all the law he ever knew on the back of a postage stamp with a black marker pen".