iPadOS 13: brightness of text changes during scrolling on iPad Pro 10,5" in Dark Mode

iPadOS 13 introduced Dark Mode and I’m trying to get used to that. However, I noticed that white text scrolling on the black background changes brightness (or “thickness”?) while scrolling on my iPad Pro 10,5", for example in Reeder 4 and Tweetbot 5, which both support native Dark Mode in iPadOS.

Is this a known (software/hardware) issue? Or is my iPad defective?