The Dark Lord hasn't visited the Manor in years. Since the house was effectively his headquarters before the Battle of Hogwarts, he felt it too dangerous to stay there once the Resistance had formed. The risk that Potter would suspect him there and set his rebels on him and his followers seemed too great. Still, it makes sense that he would want to hold this so-called crisis meeting there, given that the majority of his closest confidants are there. First and foremost the Lestranges. I don't doubt for a second that Theo is telling the truth.