I think TLA means “Three Letter Acronym” in some circles. So like, DBA would be a TLA meaning “database administrator” for example. Didn’t read the article to get the context though, so not sure if it fits

I don’t have much experience in the realm of gpg. My experience is mostly with TLS. From what I know, if you’re doing client authentication, you encrypt your message with your private key, and then the public key on a cert is used for validating that the message actually came from you.

I think code signing is similar to client auth, but not positive. Again, I use TLS, but I’m not a professional

https://about.signpath.io/code-signing/theory#%3A~%3Atext=Software+publishers+use+a+secret%2Cpart+of+the+distribution+package.

Edit:

What I found from Wikipedia:

The client sends a CertificateVerify message, which is a signature over the previous handshake messages using the client’s certificate’s private key. This signature can be verified by using the client’s certificate’s public key. This lets the server know that the client has access to the private key of the certificate and thus owns the certificate.

https://en.m.wikipedia.org/wiki/Transport_Layer_Security#Client-authenticated_TLS_handshake

I think encrypting with a public key is mostly used in client -> server traffic (client encrypts with server’s public key, server decrypts with private), and not code signing. However, I’m no TLS/asymmetric crypto savant.