Not a fact, it’s just a fan theory that gets endlessly repeated and is probably false. I’ve heard it several times before and there’s no evidence to support it. The problem I have with this reductive approach, boiling an author down to nothing more than just regurgitating their own life events, is that it removes the possibility of a collaborative effort. Maybe he got the idea of the giant spider from someone else?
I’ve never actually poured a casting myself. We did use a caster at one stage that used centrifugal casting and they were a nightmare to finish. If I was making a band like OP’s like a one-off, I’d roll a strip and turn it on the mandrel and laser the join.