There are a couple of situations where this could be advantageous.

First is an uprange start, unless it specifies head position that prevents you from looking down. You can't look at the target anyway so might as well look somewhere else beneficial. Obviously, at the buzzer you have to snap your head to the target.

Second is any unusual start position that you may have not worked out in dry fire or practice. Having to keep arms stretched or placed somewhere per stage requirements, having to open the door, getting up from a chair, I even seen people do it for a surrender draw if they felt rusty that way. If you're not sure you can draw under such or similar circumstances smoothly, a match is not the time to figure it out. It is a simple math decision. Unless you're shooting a classifier or some 12+ HF stage, average draw vs blazing draw doesn't cost you a lot. Getting a crappy grip, which likely will be slow anyway, with subsequent bad hits does.