I hate to admit it, but given the financial state of print magazines, in general, I don't think that sharing editorials, cover subjects, and other content is a bad decision, from a business standpoint.
Of the major titles that still have big circulation numbers, how many people buying the magazine are buying or have ever bought multiple editions with any regularity, if at all? I'd wager it's a very small number, a tiny fraction of overall readership. Your average person picking up a copy of Vogue in the supermarket, train station, or airport because Adele's on the cover or they just need something to flip through likely has no idea (and wouldn't care if they did) that one of the editorials inside is also in British Vogue, Spanish Vogue, and Italian Vogue. A more invested consumer of magazines may know, but will it stop them from purchasing? It didn't stop me, I wanted both covers. I'll certainly be getting British Vogue and Italian Vogue's Gaga covers. I got both Adele covers despite the shared cover subject and a shared editorial inside. I may be *annoyed* that I'll have multiple copies of issues with the same editorial, but my need to own all the Gaga covers outweighs that. Stan behavior. Models in these shared editorials are probably happy that they can add more titles appeared in to their resume and get increased exposure, the magazines save money on production, and if the editorial is half decent, it may be the best thing in the issue, even if it's shared. Another factor (maybe it's a cynical take, but I think it's true) is that magazines are trying to be seen as welcoming diversity and being more inclusive. A large, well-done editorial featuring a couple of Black models, a plus-sized model, etc. that they can all share is a lazy but likely effective shortcut to achieving that goal.