And thus the time has come. With Min Min's release, and players now seeing that she has a separate fighter spirit (despite already having a spirit in base game), this should be a reminder to the nature of toys. By the nature of toys I mean that for various brands and franchises, countless of toy iterations are created (i.e. collectible figurines, plushies, LEGOs, and even video games). One can even see different styles of one same branded toy (a taller action figure, and its miniature replica). To top it off, something that collecting spirits time and time again demonstrate, an 'x' number of copies of said toys are produced.
Min Min has come and dashed the spirit fan rule yet, it would seem that it never existed to begin with. Note that in the base game, upon completing the World of Light campaign, the spirits are 'freed', which could be interpreted as characters no longer being bound to being mere spirits.