No, the spokes are not too short, some spokes extend fraction of a millimeter beyond the nipple end, but they are generally even.

Given a spoke of "correct" length with 9mm of thread, a nipple with 10mm of thread will cause the spoke to bind 1mm before the spoke reaches the end of the nipple, yes? In this case, a shorter thread of say 8.5mm would be preferable. Is that reasoning correct?

The DT Swiss 12mm nipple has a thread of 8.55mm and their 14mm nipple has a thread of 9.75mm. The 12mm nipple is fine, but the 14mm would bottom out/bind on my 9mm threaded spoke 0.75mm before the spoke end reaches the end of the nipple.