It is very important to fully control image processing from the sensor to the final file to get consistent results and there is nothing better on Earth to demonstrate that than smartphone image processing which can do all kinds of adjustments including, famously, detecting Moon presence in the frame and pasting pre-rendered moon on top of it.

Without knowing which camera program you used (and each program is free to apply any processing) it is overwhelmingly likely that your camera program applied some reconstruction algorithm (probably involving machine learning) which produces these artifacts because
I do not know any other ways to get this image defect (noise/dirt/lens damage).

You can get more understanding of what's happening if you do series of photographs of same chart and reducing the distance. At some distance you will clearly see that processing algorithm stops introducing fake image details. You can also try tilting the chart or rotating it and result will very likely change.