P: Export As... does not export as expected however Save for Web (Legacy) does work as expected
PhotoShop Mac 21.2.3
Macbok Pro Mid 2015 Catalina 10.15.7

This is what the layout looks like. The images are smart objects. The .psb files have multiple layers and the top layer is the desired image for the composite image. This is what the layers panel in the psb looks like:

This is what the Export as... exports

This is what the Legacy export exports

