Yeah, this is fundamentally expected behavior but the results can vary wildly based on how much of a gap there is between available information and the 'resolution' of the desired output.

I feel like managing the level of information available and judging if its sufficient to make an extension of details lead to a reasonable outcome is the responsibility of the human/user more than the AI. If half the image is destroyed, it is less of a restoration and more of an imagination but the process is the same as if it just had some scuff marks to buff out. Its on the person using the tool to recognize the extent of impact that using the tool is having and to communicate that extent when discussing the results.

otherwise i could give the "restoration process" a torn corner of a photo from my great grandmas house and after it completely makes up a photo i call it restored