Yes. For example you could hook the function that encrypts the outgoing payload and print it out before it is encrypted. And then for decryption you could hook the function that decrypts the payload as it comes in print out the result.

Going further, the API likely uses some secret key for encryption/decryption and you could hook that value out of the app as well.

Wow, that sounds really cool! Searching around i found this list: https://github.com/dweinstein/awesome-frida