If they want to sell them on Catalina and newer devices they surely need to follow similar steps anyway, while paying for infrastructure themselves.

https://developer.apple.com/news/?id=09032019a

You don’t have to have a paid developer account for app signing, your app is never reviewed by a human, and Apple doesn’t get a cut of your app sales.

So how is it “similar”?

> Please note that you must be the Account Holder of your development team in the Apple Developer Program.

https://developer.apple.com/developer-id/

> You can only notarize apps that you sign with a Developer ID certificate. If you use any other certificate—like a Mac App Distribution certificate, or a self-signed certificate—notarization fails

https://developer.apple.com/documentation/security/notarizin...

That similar.

You can have an Apple developer account without paying for it, there’s a free tier, and I think that is allowed for what your parent is referring to.

I have an Apple developer account...

So do I and I don't pay for it, and I can sign my apps. What's different in your case?

So now developer certificates are available on the free tier?

For at least a few years, they have been. You can set a team and a signing certificate in Xcode with a normal developer account, which does not require any payment. To publish on the App Store, however, requires a paid account.

Sounds like you don't use that dev account much :)