Screenshots get different treatment
A screen capture is not a photograph. It has flat backgrounds, hard edges and no sensor noise, so the contrast stretching and thresholding that rescue a phone photo would only degrade it. OCR2text detects this from the image itself — colour count, edge sharpness, background flatness — and leaves a clean capture alone.
Light text on a dark background is the one case where a screenshot does need work. That gets inverted automatically, and Auto enhance tells you it did so.