KIP15: User Rejects CommandSigData -> noSig or failure?

[Luzzotica]

Hypothetical situation:

3 CommandSigDatas are sent and the wallet.
The user signs 2 of them and rejects the last one.
Should the wallet respond with noSig for the last CommandSigData?
I feel that sometimes there might be a noSig just because the wallet doesn't have a private key for any of the listed public keys. Should the dApp expect the same behavior for both?
Or perhaps the wallet should respond with failure if the user rejects the request?

Can we perhaps add some clarity to how the wallet should respond in the above situation?

For now, I will use failure so I can provide feedback in the msg field.