Tabbed text will always be treated as code rather than text, even if you alter the CSS so that they look the same.
It’s just an example of the primacy of code in markdown. Ditto ‘text editors’ are code editors rather than text editors.
It’s a different evolutionary line to word processors, notepads, two pane outliners etc, such as Scrivener and most programs for writers.
And that is different again to to the line of wiki type outliners such as Workflowy, Dynalist, and now Roam.