This doesn't sound very likely. In order to show pixels on a screen, something has to write those numbers somewhere. Screenshot should be writing those pixels to a file as an image format, not consulting whatever programs are running to ask if there are areas that they don't want to draw.
The pixels are literally encrypted on PCIe on their way over to the GPU, it's quite draconian. Been this way since Vista ("Blu-ray is a bag of hurt" - Steve Jobs)
