Hello  actually I found my statement here from the great French typographer JeanPierre Lacroux who cites the source I gave you paragraph   For your question JeanPierre Lacroux defines the em as it is defined in the Wikipedia article so the answer to your question  is clearly no Now for your question  I cannot answer based on what JeanPierre Lacroux says and I dont have access to his source which is one of the most reliable source for French typography