Is it correct that more than 160 bits of input data for producing a private key are superfluous?
No, that's not correct at all. If someone knew that your private key contained 96 zero bits, their search space would be drastically reduced. 256-bit private keys are used because they are the minimum considered sufficient to provide the level of ECDSA security required. 160-bits can be used in the hash function because hash functions get more security per bit than ECDSA does.

You could, however, use 160-bits as a seed to generate a 256-bit ECDSA private key. For example, you could use a SHA-256 hash of a 160-bit seed as your private key with no loss of security. You can even go down to 128-bits with no significant loss of security.