It's certainly possible to get timbers that long, especially if their cross section is smaller, such as a common rafter. I can't tell exactly what's going on in your example, but it's possible that the rafters are discontinuous at the purlin plate, but I doubt it. Especially as this is a reclaimed structure, where the timbers were cut long ago when larger trees were more plentiful. But again, even today, getting timbers that long in douglas fir, for example, is not a big deal. CB.