I would think that there would have to be some accounting for the target's course/torpedo track angle.
Some calculations I had worked up at one point show a lead angle of 29 degrees for a 26 knot target at a track angle of 90 degrees is about right, if the sub were firing a high-speed Mark 14. For a Mark 10 that an S-boat would be using, the angle would be too small. My math shows about a 36 degree lead.
Set up a right triangle. The right angle is your track angle. The hypotenuse is your sighting line. Side A (target travel) is length 26 (speed of target). Side B (torpedo travel) is length 36 (speed of a Mark 10). A/B = tangent of the lead angle.
A/B = 26/36 = 0.72222...
Inverse tangent of 0.72222... is 35.83765 degrees.
:. the 29 degree lead angle shot will pass ahead of the target.
(Remember when you asked "When will I ever use trigonometry after school?"

)