Function sighash_v4_raw 

pub(crate) fn sighash_v4_raw(
    precomputed_tx_data: &PrecomputedTxData,
    raw_hash_type: u8,
    input_index_script_code: Option<(usize, Vec<u8>)>,
) -> SigHash

Compute a pre-V5 (V4) signature hash using the raw hash_type byte.

zcashd serializes the full raw byte into the V4 sighash preimage and only masks with SIGHASH_MASK (0x1f) for selection logic. Callers handling V5+ transactions must use sighash instead so ZIP-244 strictness is enforced.