As stated in the following issue on GitHub, the commonName of the certificates being generated by the internal CA (Caddy CA or imported one) are empty. One of the developers mentioned that his is common practice for this type of software, as using commonName for verification is deprecated. Also, he noted that it is bad code to fill in this code as it is not advisable to do so.
Nonetheless, I think there should be a option in the tls section or in the global section which allows us to set the commonName to something like the SAN, the main argument being retroactive compatibility (and it does not cost us anything to make such an effort).
As a additional benefit, the certificates will display in Firefox and in Chromium with a name, as at the moment there is a white blank which is quite bothersome. I also read and share the opinion of the dev, as this issue shall be fixed by the developers of the certificate viewer, but it can be easily fixable by implementing such option for anyone who just wants to enable it.
If you have any other points to make, please, feel free to educate/illustrate me so.