If Lucasfilm continues to have to go to fan restorations they found on YouTube over actually restoring the film, then there’s something wrong there. Film history is being ignored because fans posted clips somewhere? What if they accidentally use Revisited or any of the other fan edits that are right next to it online? Why would they know to reference Legacy if they didn’t have Legacy on hand?
Film History isn’t being ignored. There’s a considerable difference between a film being restored or preserved and a film being sold on a home video format of choice. One is a question of preservation, the other is a question of consumerism. You may ask “well what good is preservation if I can’t buy a copy of it at the store” and I get that question, but film history isn’t being ignored, and the original version of Star Wars isn’t going to disappear from history because it wasn’t pressed onto 4k UHD disc.
I would suggest we’re seeing that screencap used in that book because the book is low-priority tie-in merch handled by an outside company and editorial oversight isn’t as stringent as it was for Rinzler’s books. That’s similar to CNN’s docu-series having someone use a clip from Despecialized. These sorts of discrepancies happen frequently at many other companies, too - video game companies using google searches for material instead of going into their own archives is an example off the top of my head. Lucasfilm/Disney isn’t necessarily immune to such things.