Just because people are not swapping configurations daily or weekly doesn’t mean modularity is not valuable, especially for institutional users. If one of my officers buys a personal P320 and decides they want a bigger or smaller gun it’s a matter of buying the appropriate OEM parts, having an instructor or armorer swap it out, and shooting a qualification with the new configuration. As opposed to having to D authorize the old gun then do an armor inspection, qualification And the administrative process of getting a new gun approved in the system.
Having small medium and large sizes of various configurations is also useful given our last three issued duty guns have been one size fits all.