Distance setting in TDC useless?

[Hylarion]

Hi all,

I am still wondering what's the use of setting the distance target in the TDC (I play 100% realism btw)?
From what i understand, it has no effect at all on the solution (for math addicts, it is based on Thales theorem , for others, just change the distance setting, you'll see it has no influence at all on the gyroangle solution).
Would it be somehow related to the max time the torpedo runs before it triggers automatically its pistol? So far, the best use i've found of this is to get an estimate of the expected time to impact (the red needle on the chronograph)

Just wondering if someone has a clue...