For Importing Keys, in the real world we should be using SHA 256, shouldn’t we?

Correct SHA – 1 is said to be "Good Enough" for a one time use like in the LAB and SHA-2 is better still and perhaps a better habit to establish — here is how to update the LAB.  

Source AWS:  https://aws.amazon.com/premiumsupport/knowledge-center/invalidciphertext-kms/

By default, OpenSSL uses the SHA-1 hash function.

To avoid import errors when you use the RSAES_OAEP_SHA_256 algorithm (SHA-256 hash function), encrypt your key material with OpenSSL using the openssl pkeyutl command and specify the parameters –pkeyopt rsa_padding_mode:oaep and –pkeyopt rsa_oaep_md:sha256.