I don't know if this was ever posted or if anyone noticed (I didn't as well until now) but Lor'themar knew Sylvanas for a very long time
Old Allies quest https://wow.gamepedia.com/Old_Allies
this would make Sylvanas a few thousand years old.Sylvanas was my Ranger-General. I have respected her for millennia. Making this choice is something I have been wrestling with for some time. Baine's death will tear the Horde apart. The Tauren will not stand for it and if they leave, I know they will not be the last.
We must save Baine. Not just for his life, but for the Horde. I can only hope once the time pressure is gone we may be able to reason with her but...
I have contacted allies who will help. Meet them in the Cleft of Shadows.
it also confirms that Alleria fought in the Troll Wars.
that or writers made a mistake as usual.