This is not true. Some schools count it as demonstrated interest and as such, expect it. (I don’t know if Dartmouth does this)
I would think the vast majority of Dartmouth applicants have updates they can come up with. Grades, tying something they learned to a class and/or a prof’s research they would like to participate in, EC updates, etc.
Many HS and private counselors encourage deferred students to send LOCI (if allowed).