In the file below, trying to UntrimHoles the center hole makes the whole part go away except for one surface. Probably because the bottom part of the hole crosses a surface seam. Checked both in V8 and the WIP. One for the “can improve” list.
DeleteHoleBug.3dm (3.3 MB)
I guess deletehole keeps deleting until it finds a surface with an internal trim. In this case that means only the top face remains.
I agree it would be nice if these kind of untrims across seams would work. I imagine though that it would rather become a removeface command where you need to select all the faces you want to eliminate from the model.
I don’t see why that could not be automated, since Untrim on the extracted bottom surfaces works.
Edit: this is the YT that has a similar case, yet more complex
RH-31973 Untrim - intelligent ‘remove feature’ feature