Author here. Was building an indexer to correlate Hyperliquid L1 transfers with HyperEVM transactions. The official RPC gave me one hash, but block explorers couldn't find it.

Turns out: Hyperliquid publishes block data to S3, and system transactions don't have hashes. nanoreth (which explorers use) has to recompute them, but uses a different encoding convention. they stuff the system address into the signature field as a "pseudo transaction."

Neither is wrong exactly, but if you're building tooling you need to know which convention your data source uses.