As someone who is watching the speedruns, I too think there should be a whole different category for classic%, how i view it its supposed to be just LOD and no changing to classic d2 and this means if you start with a classic char then it should be just classic% and if you change to LOD mid-run it invalidates the run. Since this is not a bug/glitch that you can abuse to skip its not cheating or anything, its just feels off to just do 80% of the run on classic and then just switch to LOD at the end of the run even though i know any% means go as fast as possible to kill hell baal.

Again this is just my personal opinion in this, the admins/mods can decide however they should think best of it.