This chapter actually explained it! Yura has his spiritual energy inside Magatsumi, so he can use its power remotely as long as the Sword Saint activates it for him. As for why the Sword Saint is willing to activate Magatsumi for anyone who wants to wield it, I'm not so sure

One of the best pages in the series

Not the same. Hokazono isn't suffering from health issues, he's just heavily overworked by Jump right now