The layers of extreme complexity in this situation are astounding.

The app has some text internally, it renders it by rasterizing fonts to a bitmap, the OS takes the bitmap and composites it within the wider UI. Google Assistant grabs a screenshot of the fully composited, post-processed OS UI, sends it over the internet to a server, which uses an OCR model to read all the text, and a different model to work out which is the relevant text, which is then sent back over the internet and displayed on the device.

All so the user can copy some text.