We had a room in the house that had a whole wall of books. There was a carpet on the floor. As a child I would wander in and become slowly transfixed by covers and just the pattern of the whole thing. I tried and failed many times to read books there, often falling back to simpler children’s encyclopedias. With perseverance I became able to infer word meanings through context (a skill that remains today), and slowly but surely titles were conquered one by one. Im eternally grateful to my grandfather for reading so much to me as an extremely young child and to my father who stocked that study with the equivalent of the best wine available. I don’t think that experience would have been possible with the kindle I now own :)

At an early age it is important to have contact with physical objects. (And no, an iPad wouldn't cut it.)

I think it is important at any age. I've been reading on a Kindle or iPad for years. My daughter recently bought a physical book for me and I had a hard time reading it. I've never had a difficult time diving into a book, but reading a physical book after using a kindle for so long made immersing my mind into the book quite challenging for some reason. I bought some other physical books the other day to see if the issue was just the story I was reading or if there is indeed an aspect of reading physical books that has atrophied in my brain after using electronic books for so long. If the latter, that would be quite concerning to me.

Perhaps completely irrelevant as long as an equal number are read?

Maybe, maybe not. These social studies are so poorly executed that you're just waiting for them to be debunked.