Hash written to the blockchain is not prefixed by zeros or not at all but is dublicated (thats why it seems to work, but that measn double the gas price and or incorrect formatting)

[FantasticoFox]

See https://sepolia.etherscan.io/tx/0x7f878f524b7916dc818fe2c0b83ca7fbe834d22f3d745305444e786d9797724e

That is wrong:

0x9cef4ea1f57fde64054cfa553e91c67ef45f7033b58665db6d1f2d667f0755977e29dff6f57fde64054cfa553e91c67ef45f7033b58665db6d1f2d667f0755977e29dff6

Correct would be:

0x9cef4ea10000000000000000000000000000000000000000000000000000000000000000f57fde64054cfa553e91c67ef45f7033b58665db6d1f2d667f0755977e29dff6

This contract is for SHA3-512 thats teh reason why it has the spaces in the beginning.

[FantasticoFox]

I tested with the CLI and the outcome is that the hash i written without leading zeros:

That is also correct. If this means less gas-fee without leading zeros is OK and CORRECT two!
Chose the option which costs less gas.