"A start tag whose tag name is one of: "caption"..."

[JKingweb]

https://html.spec.whatwg.org/multipage/parsing.html#parsing-main-intd

A start tag whose tag name is one of:​ "caption", "col", "colgroup", "tbody", "td", "tfoot", "th", "thead", "tr"
If the stack of open elements does not have a td or th element in table scope, then this is a parse error; ignore the token. (fragment case)

As far as I can tell this case is unreachable. The only way to reach the "in cell" insertion mode is by having a <td> or <th> element in the stack; the rules for resetting the insertion mode appropriately only yield the "in cell" insertion mode if last is false (i.e. not if node is the fragment context).

Is my assessment correct? Is the text superfluous, or is the insertion mode resetting algorithm wrong?