This sounds like a custom chart that someone has designed. I can imagine how it looks with an ever-decreasing remaining scope towards a bulls-eye.
Although the regular burn-up charts are fit for purpose; I can see how an enterprising member of the team might have designed it.
The alternative explanation is that it is one of the custom charts produced by Aha! - the product roadmapping company which now offer additional services beyond their original purpose of visual product roadmaps. I have only ever used Aha in a trial basis so I cannot say for certain. I also make no recommendation for their product whatsoever.
They have various visual plans including one which looks like the following. If you cannot find your custom chart, you might be looking at something from this software vendor.