Hello actually I found my statement here from the great French typographer Jean Pierre Lacroux who cites the source I gave you paragraph 3 For your question Jean Pierre Lacroux defines the em as it is defined in the Wikipedia article so the answer to your question 2 is clearly no Now for your question 1 I can not answer based on what Jean Pierre Lacroux says and I don t have access to his source which is one of the most reliable source for French typography