`TransitionStore.terminal_total_difficulty`, otherwise this setting initializes `TransitionStore` with the specified, bypassing `compute_terminal_total_difficulty` and the use of an `anchor_pow_block`.
Except under exceptional scenarios, this setting is expected to not be used, and `terminal_total_difficulty` will operate with [default functionality](./fork.md#initializing-transition-store). Sufficient warning to the user about this exceptional configurable setting should be provided.