That column represents the minimum IT skills required to perform the installation. It doesn’t represent the suggested audience for a given method. Someone who is familiar with managing Linux and Docker is free to choose any of the four installation methods.
In contrast, someone who is not comfortable with Linux and Docker will have a challenging, potentially frustrating, experience with Supervised, Container, and Core. Even if they muddle their way through the installation, they will still be challenged by maintaining Linux.
“None” would be misleading. You need some IT skills to install Home Assistant OS (certainly more than for installing a consumer-level product like Philips Hue Bridge).