Since all the areas outside the city did not have extended night areas, they had to be created and added for BGT & BGTutu. No? So, why can't they be added for vanilla BG? I have some coding experience and this seems like a small thing in the scheme of things.
Well, the fact is the BG2 and BG1 use different game engines, the BG2 and thus as an extension the BGT & Tutu have more things put in it than the original, dah that's why the original games engine was modified to create the extension(the one running the BG2) ... thus the tools that we use have more options, and we have more things to modify.