You could technically apply this to any proof-of-work chain in principle, but only Bitcoin actually qualifies.

Every other chain inherits hindsight. They were created after Bitcoin, with full knowledge of its discovery, its incentives, its mechanics, and its success. Their “genesis” isn’t ex nihilo. Their rules are engineered responses from prior knowledge.

Bitcoin is the only chain that began without prior informational bias, the only one whose constraints weren’t shaped by market expectations or human hindsight. It’s the only ledger that didn’t know itself before it existed.

There only needs to be one longest chain to measure, it’s Bitcoin. The rest are derivatives. Everything else is downstream, contaminated, and fundamentally incapable of being Bitcoin.