Hi, [import] was part of Extended. If I am not mistaken, it worked in Extended because of some changes to the core code specific to it, hence it was never an external or did not ever work in Vanilla
[declare] is Vanilla's [import] and something that came about later, making [import] just part of history and something to be forgotten...
Many help files you find from external libraries in deken still use [import] just because it's the same file that was part of Extended and never got updated. But then, anyone can update them and reupload them.
cheers