The supply chain angle doesn't hold up though. Medieval binders were working in shops where parchment was still expensive, and waste not want not was the whole deal. If they were just grabbing random scraps, you'd see the same texts over and over in bindings from the same region, but what we actually find is wild variety, everything from old church music to household lists. That points to binders saving whatever came through the door on purpose, not just snagging bin scraps.

Did you check the rim joist area while you were down there? Everyone talks about bulkheads and windows but in these old Worcester duplexes the rim joist is usually wide open behind whatever the builder stuffed in there, and that is where you get the constant cold draft you can never quite find. Mine had nothing but a scrap of old newspaper from 1923 jammed in one bay and bare wood everywhere else. I cut rigid foam board to fit between each joist, sealed the edges with spray foam, and that alone cut my draft problem way more than the bulkhead did. It is a little more work than a Saturday afternoon but you are already in the basement with the caulk gun so it is worth a look. Also check where the chimney passes through, that gap up top pulls air all winter like a straw.