In reply to Anthony Hortin.

I think the issue more than anything is what happens when the classic editor plugin is installed. By default it disables the post block editor. For users who only want to disable the widget block editor it's a less than ideal experience to install a plugin, realise it disabled more than they desire, and then have to look for the settings to get it back to the way they want it.

It might be ok for an experienced WordPress user, but for most it's a bit easier to use a plugin that enacts the desired behavior upon installation.