Fair enough, you may not find such data.Yep, I've seen this. Have you ever seen the DJI GO app prompt you to calibrate the compass? I haven't. Nor have I seen anyone else mention it has ever prompted them to calibrate. So, I'm not sure it's wise to follow that advise.
In this article from December 21st, DJI recommends pilots should calibrate the compass before every flight because it's essential for safety. Again, I don't think it's necessary in most cases. I'm just pointing it out because DJI does not always recommend what you see in the current Spark manual.
That said, doing something unnecessary always creates risk to do something wrong. Worth it? Your call.