Photo AI latest update allow extension to be used in Mac's Photo App is a great features. The following are noted

When you upscale its resolution after editing in Photo AI and save back to Photo App, the resolution remain the same as the previous photo. Wonder if this is the feature needed to be looked into in future

What do you mean by this? Do you mean DPI or upscaling the image?

I believe that if you upscale the image you would have to reimport it into Apple Photos.