See this same thing everywhere, not just roofs. Someone slaps a fresh coat of paint on a problem and hopes nobody looks closer, whether it's a used car or a house or a job listing that sounds too good. Paying someone to actually look under the hood is almost always the cheaper move.

Wait, is that the same guy with the table near the produce stands? I think he might've been overselling the whole "page 30" rule. I grabbed a beat-up John le Carre from him last month and the damp smell was right there on page 10, but the front cover hid it totally. You're right to check, but honestly, I just give the whole book a quick sniff near the spine and flip to a random middle page before buying. That's caught more mold than any fixed page number ever would. Mold can start on any page, depends on where the water hit the stack. So yeah, keep checking, but don't trust that guy's specific number.