If your Xiaomi phone is not saving photos from WhatsApp to the Gallery, it is due to changes in the updated version of the Gallery, not a malfunction in the system.
For your reference, here are the detailed explanations:
1. In previous versions, the Gallery automatically scanned images from chat histories and saved them directly to the Gallery.
2. In the newer versions, the Gallery no longer scans chat images automatically. Photos need to be manually downloaded before they are saved and displayed in the Gallery. This can lead to the misconception that WhatsApp photos are not appearing in the Gallery.