Correct spoke length is always important but particularly so when using aluminum alloy nipples. I’ve seen many wheels where riders thought they had broken a spoke, only to then learn from me that the spoke itself had not broken. Instead, the head of the nipple had broken off, rattling around in the inside of the rim while the intact spoke was dangling with only the shaft of the nipple still attached. A brass nipple probably would not have broken in the same circumstances, but the head of an aluminum nipple must be reinforced by the threaded spoke extending all the way through the nipple, preferably to the end of the slot. Otherwise, the head is vulnerable to snapping off, something I have seen in a distressing number of instances, often on factory build wheels. Some of them have been pretty expensive, high-end wheels.