It's the Let's Encrypt people who make certbot, so that's just an implementation detail, and the premise here anyway is that you would be doing it manually (once) because the inconvenience to be avoided is when certbot can't update the DNS records automatically.
No, it's not the LetsEncrypt people who make certbot. Certbot is an EFF project, managed by separate people. Additionally, most of the DNS implementations will require the use of a specific plug-in/library for your selected DNS platform, and those, also, are developed separately.
Let's Encrypt was an EFF project to begin with. They're still the same people.
The DNS plugins only matter if you're trying to automate updating the DNS entry. The whole point is that you could have certbot spit out a DNS TXT record for the user to manually add to their DNS once, e.g. which contains the public key fingerprint of the certificate they want Let's Encrypt to renew on an ongoing basis, and then certbot would be able to renew the certificate as long as the DNS record remains in place.
No, LetsEncrypt was not an EFF project to begin with. Look, it works how it's documented to work. If you wish it worked some other way, to solve your particular suggested workflow, you're likely free to fork it and make it work that way.
