Light refraction, generally, has a lot to do with POI considerations.
Here is a perfect example I have used with several witnesses with dropped jaws.
For years, We shot nothing but LCS 40's-45's and before that 36's, until the March's hit the USA and after a bit, bought my first one.
I forgot who exactly told me to try this test but I set my gun up at 200 at the IBS 200-300 nationals well before the match in mid summer and centered the dot right in the mothball and left it there for 5 minutes plus so many view. and as you looked for a minute or so you could watch that dot slowly drift out almost to the 9 ring, more than once. The LCS set up next-door barely budged.
This is one of THE principle reasons guys like Tony B began to advocate getting all your shots in a group fired in no more than 20-30 seconds unless you get caught in a switch and have to go to the sighter. If you're a picker it's easier to get caught out.The farther the distance, the more important because, loosely translated, your scope is no longer looking where your barrel is pointing.
Remember in BR matches we're only talking, generally, a couple bullet holes, but it is a substantial factor, often...not always, but often.