I also disagree about the "beholder words"; to me "it was surprisingly low" means "I am drawing your attention to the fact that the low value surprised me" rather than "you need to be surprised by the low value".
I agree with your interpretation, but here the issue is that "beholder words" don't give the reader the information necessary for them to make their own judgment. Readers are left thinking "ok, but how low is 'surprisingly low?'" Writers should tell the reader the exact number, saying "surprisingly" communicates nothing because it's relative.
my reasoning is that the former is more of a parenthetical, as much as to say "the results were low (and it surprised us)", rather than putting the "us" who were surprised front and centre and making the low results subordinate to that.