Tabooing "truth", one can see that the theories really speak about (slightly) different concepts.

Then, you would merely choose which of the concepts is the one needed for a particular theoretical purpose. Right?

Wrong! The arguments go to the concepts' coherence. This is why it's philosophy, not lexicography.

For example, a correspondence theorist generally argues that the notion of an epistemological limit to which scientific findings converge need not exist and can never be established empirically. If correspondence theory is true, you aren't allowed to use the Piercian limit. It's a vacuous concept.

Or, the correspondence theorist argues that the epistemological limit of scientific investigation can't even be defined without assuming a correspondence variety of truth (which the Piercian, in turn, argues can't exist). The correspondentist argues that if you define truth at a limit, then you have to define the truth that science is converging as itself the result of a scientific investigation at an endpoint, and similarly for the concepts you use to define scientific investigation, etc. Thus, a Piercian view, it's contended, produces an infinite regress.

It's possible that both concepts are coherent, but that too would require a philosophical argument--and it's an unlikely result here, at least in my opinion: it's probably more likely that both concepts are incoherent than that both are coherent.

These kinds of conclusions, philosophical and lacking in direct application, help inform the priors one assigns to just about every scientific controversy.