Just realized this game essentially has to be a sequel to XY if they actually want to do meaningful game design with Megas in the campaign this time. The whole thing with them in that game was that they were this rare, mysterious, poorly understood thing that was just being newly researched and looked into. Therefore it would follow that prequel material cannot contradict this: You could get away with saying that the knowledge was lost to time if this was untold centuries ago in some ancient forgotten era of legends or if it was like Hisui where it's in a really undeveloped era with little in the way of civilization to document things but even the farthest back estimates by fans put this in the Pokemon equivalent of the late 19th century which is nowhere near enough for that explanation to be viable.
Well, doesn't matter either way. I looked into the "woman using smartphone" claim from earlier and
at this timecode you can definitely see they are at some sort of smart device, being able to make out typing motions if you pay close enough attention.