I think it is something like this: Even the lowest-level Shimano stuff is going to work, which is unsurprising, seeing as derailleurs have been around for so long ..... Sure, the quality of materials is pretty low, but no one is buying anything Really Shimano and finding it doesn't work at all.
Of course, given that derailleur tech is so old, pretty much any derailleur is going to work a t least passably. However .... For the tiny percentage of people who know the name, the Shimano decal is more a graphic, just decoration .... Look how many ProTour bikes (and mass-market expensive bikes) have the manufacturer's name in big letters down the down tube----but since no one has ever heard of whichever random Chinese Communist factory produced the frame for whatever Taiwanese corporation was contracted to produce the frames .... so "Shimano" is mostly just a flashy imitation of "Look" or "Cervelo" or something .... but it is a real "bike company" name.