The 20% is for a reallocation of the
point charts - where the total points at the resort cannot change, but
DVC can reallocate the points required by raising some nights and lowering others. As long as the points required for the entire year are in balance, they are allowed to modify seasons, weeknights, weekends for each room type - and have done so in the past.
The DVC documents have a maximum reallocation chart to show what the required points would be if the points were balanced thru the entire year for each type of villa (weekends/weekdays would all be the same as well as no seasonal variation - the only difference would be for Studios, 1BRs, 2BRs and GVs as appropriate for each resort).