In vanilla BG1, all the area files have scripts assigned, even if the referenced script file doesn't exist. This is super-convenient for modding, because if I want to add an area script, I just have WeiDU compile the script (and EXTEND_BOTTOM is smart enough to compile a new script if the referenced script to extend doesn't exist).
NTotSC decided to "clean up" all the area files and get rid of the script references for areas where the script file does not exist. That's why Wilton and Corianna are "missing". The CREs were copied over, the scripts were compiled to add them, but the areas don't call the scripts because NTotSC removed the references.
EDIT: I can borrow a file from BG1NPC to assign the area scripts. But, time for sleep now...