The claimed stat seems more ambiguous to me on which of those possibilities is the case. It's specifically citations to old papers that are increasing. That is

The claimed stat seems more ambiguous to me on which of those possibilities is the case. It's specifically citations to old papers that are increasing. That is the original old papers, not just their results. Citing old results "updated" or "collected", in e.g. a modern textbook or survey article is one thing, and could more plausibly be divorced from the history of science. But if people are really reading (vs. just blindly citing, which may be the case) old scientific papers, that seems more to me like the history of science, in at least a somewhat broader sense, is poking its way into modern science more significantly than it used to. When you read the original papers, they come along with their whole historical era, all the way down to the quirks of language, notation, problem framing, epistemological assumptions, etc. You even, sometimes, need to know something about the history-of-science as a field to correctly read and interpret a paper from a different era, which you probably want to do if you are really citing it for significant content. (Admittedly, a lot of the citations are probably throwaway cites to old papers the authors haven't themselves read, along the lines of "This was first studied in 1927 [1]". In that case someone still needs to do some history-of-science work to read this 1927 paper and characterize it accurately as "first" to study some problem... but that work might be done by someone else.)