This is called 'incremental reading' and techniques around this have been developed by research/development from the person who wrote supermemo (the closed source anki predecessor).
Thanks for the keywords — looks like some tooling already exists for this (https://ankiweb.net/shared/info/935264945), though it’s mostly focused on articles. Gotta do some more research on this.
It’s closely related, but I suspect that Dr. Wozniak would consider my implementation to not be “true” incremental reading: There’s no attempt to progressively distill passages down into more traditional flashcards, and a fixed rate of new material; There are almost certainly other differences as well.