I think some of this is starting to come into focus. It appears the way these keys are commonly stored necessitates careful treatment after generation. For instance, if this reference is accurate, an RSA private key in PKCS#1 includes the p and q prime factors on which the whole security of the key pairs depends, so you certainly would not want to mix up the files: https://crypto.stackexchange.com/a/79606
It sounds like my misunderstanding. So is this just a nomenclature mix up? I'll have to do more research, because I am under the impression there is something special about the private key other than the fact it was designated as such at generation time. I have many holes to fill in my knowledge around this.
Your docs say: client uses private key to encrypt -> server uses public key to decrypt.
Do you mean: client uses private key to sign -> server uses public key to verify?
My understanding is private keys decrypt/sign and public keys encrypt/verify. Either your usage, your docs, or my understanding seem to be wrong. I think I'll stick with fwknop for now.
For example: https://keesystems.com/product-category/fittings/kee-klamp/?...