spendScript[Ref] datum parameter purpose?

[KristianBalaj]

What's the purpose of the Datum parameter since the actually used datum that is sent to validator is the actual one that is attached to the UTXO?

plutus-simple-model/psm/src/Plutus/Model/Contract.hs

Line 467 in 450e278

spendScript ::

I.e. when I have a UTXO at the script address with datum "BUM" and use the on this UTXO:

spendScript script oref () "Hello"

Then when I send the transaction, the datum that arrives to the validator is the "BUM" datum instead of the "Hello" datum.

Maybe the Datum parameter could be removed to prevent confusion?