If I'm reading this right, fractures are actually more prevalent these days?

There isn't enough information to be sure - we need to know more about the life expectancy of the medieval subjects and the likelihood of multiple fractures. Eyeballing it suggests yes, but within a factor of 2 either way.

Note though that the modern study involved older adults (50-79) who I would guess are more likely to get fractures: osteoporosis and weakened joints outweigh the increased risk from physical activity of younger people.