Since it is typical for the journal to send reviewer comments to the author(s) and there is no suggestion here that it hasn't been done in this case, "Minor Review" might be nothing more than noise, or encouragement to the author. They might disagree on impact, of course, and the revisions suggested might be easy to make. You haven't indicated otherwise. And, you are making an assumption on how they came to that characterization. Your disagreement is fine, but don't be so sure you know how they arrived at it. But the characterization itself has no actual impact on future decisions.
I would only be concerned if the editor allowed the authors to ignore reviewer comments, whether the characterization was major or minor revision. You won't know that unless and until you see the next version.
Yes, you can express your "surprise" or even disappointment in the characterization, though I think it itthat the characterization, as such, is largely meaningless without knowing more. You can also refuse to review for this journal in the future. Neither of those is a problem.