50 MB feels too low, unless the quote meant text up until the 20th century, in which case it feels much more believable. In terms of text production and publishing, we're still riding an exponent, so a couple orders of magnitude increase between 1899 and 2025 is not surprising.
(Talking about S-curves is all the hotness these days, but I feel it's usually a way to avoid understanding what exponential growth means - if one assumes we're past the inflection point, one can wave their hands and pretend the change is linear, and continue to not understand it.)