I do not make/teach Allemande as a mother sauce,but as a volute small sauce with a liaison and lemon.
Espagnol and veal stock are reduced in equal parts to produce demi glace
Reduced/fortified stock is not demi glace, perhaps glace de viande would be more appropriate. My personal favorite reduction is making a fond de veau jus lie (very intense)
I don't make as much demi these days as i find it cloudy,and pure reductions offer a cleaner/clearer plate presentation without scarifying flavor.
Time moves on as you noted with Pelliprat and Waters/Towers. Careme had his meres,but I believe in what we think of as classic mother sauces and what is taught, Escoffiers is the norm. Great thread BDL
Kuan, with all do respect, Demi glace is not brown gravey (well maybe technically)
but you know what I mean