It is plain text.
But the font wrappers you describe are part of the note. Plain text is text without display attributes.
On a Mac, for example, if you copy out of a text editor (e.g. BBEdit) and use a tool to inspect the clipboard where the copied text is, you will see plain text (aka text without formatting or layout properties).
If you copy text out of Evernote in a note that you have created without formatting, even after you "Make Plain Text," and you use a tool to inspect the clipboard, you will see formatted text, not plain text.
A plain text note would not just look like plain text (like now, where a monospaced font is applied and saved as part of the note) but actually be plain text. Yes, there would be a setting in Evernote that I want plain text to all display using AnadaleMono 12pt, but that would be an attribute of the application's display logic, not an attribute of a note.
While some apps have "Paste and Match style" or "Paste as plain text," a majority of the ones I use do not, so I need this plain-text-note feature. @CalS this is the "something different" that I want, and @PinkElephant, it is different than plain text with associated formatting that makes it look "plain-text-y".
And @jefito is looking at the issue the way I see it. If I could create a new note that was just some text in-between the <en-note></en-note> and not font/html/etc. tags, and when I paste text into it, no formatting was pasted in, and when I copy out there is no font/display metadata mixed in, then EN would have the plain text functionality I would like.
If I paste plain text (real plain text, like from a text editor) into an EN note that I have "Make Plain Text" on, and paste or paste-match-style, and copy from that note, and paste into Word, I will get font and size stuff pasted in with it. If I paste directly from a text editor, I do not get any new font/size studd pasted in.