With the blades ending at one's navel.
^ Or so they say. A tad short for me (I have a long torso, imagine an eel with a JFK haircut) and yet it was a detail picked up on by Kevin R. for his DSMD photo shoots.
... Ahhhhhhhhh - This needs to be deconstructed...
In the age of the high rise Trou. the short tie made sense. It's a hangover from then.
Rises are lower now and so Ivy ties are worn longer. Nature abhors a vacuum... "Mind the Gap"!
OR
The short tie with the skinny knot is a coded identifier?
Personally, I'll still land my upper blade within calling distance of my belt buckle.
Yous?
Another thought is that with a waistcoat (don't say 'vest', if you can help it) the tie's length is moot. Again this is a hangover from yore.
https://images-na.ssl-images-amazon.com/images/I/21C8JNS8G8L._SL110_.jpg
In my case the tip of the ( modern ) tie just touches the fly... four-in-hand knot....
Never any lower than the middle of the belt buckle, a little higher if I can wangle it. But so often, not me but the tie decides.
The 'tie to the middle of the belt buckle' thing sounds like a businesswear 'rule' to me.