Photoshop automatically optimizing by deleting hidden parts of images?

I've had a problem with Photoshop for quite some time that I've never been able to find an answer to.

Photoshop for some reason optimizes images when saving them, as in it deletes hidden parts of an image to save space.

An example:

My layer is a solid color.

My mask is a circle, which is applied to the above layer.

When I save the image and I remove the layer mask transparency, this is the new image.

I've tried saving the image to multiple formats, which doesn't seem to make a difference. PNG, TGA, TIF etc.

Does anyone know if it's possible to disable this "feature" ?

For the people who want to try it themselves, I've attached a PSD file to this topic. Simply open this file and save it as another format. Open the newly saved file and go to Layer > Layer Mask > From Transparency. This will seperate the image and the mask and you should be able to see the difference.