I always thought that the Belmonts were just that fast, and ran outside in the time (usually seconds) that the castle crumbles. Think about it, they're slaying all kinds of monsters and bosses, while exploring a huge castle all in one night. Simon's running and jumping speed is pretty apparent in Chronicles, where the falling bridge pieces seem so slow in comparison. Ditto to Richter doing the same in Rondo of Blood. I've never seen a Belmont using teleport magic, which is what Alucard/Soma presumably used as well as Julia after CoD.