While I do know trimming is pretty bad, I can see where you’re coming from but it can go both ways.
Like you said, it's more like damaging a comic than "restoring" it. I understand that since you would be removing paper from the Cap #1 and you’re not restoring or replacing that missing paper, you would just be ruining a perfectly good book.
Whereas I can see how it would be considered restoration since you’re altering the Cap #1 to improve its appearance, which is something that’s typically done when people choose to restore books.