I use the double tweet quite a bit. Usually not on beckoning subs however. My double tweets usually occur on
travels, if a player "unexpectedly" steps out of bounds.
Example;
Saturday, as player A1 steps back to shoot a 3 pointer, he stepped on the line. "tweet,tweet!"
As I said, certain travel situations,
as well as basket interference and goaltendings.
I think it says that something happened that stops what may look like a normal play from continuing.
Am I making sense?