I have been frustrated by the number of questions being asked regarding the Out of Sequence imports especially when time lapse sequences are involved.
It appears that the sort order (Time, File Name, Media type) has nothing to do with the sorting of images during the import stage but is solely used to display images in the requested sequence.
When I import images from the CF (card is always formatted after a copy to the PC) the imported sequence was the same as the captured time sequence (as well as the File Name sequence). When I copied files from the CF card onto the hard disk and then imported them, the images where imported 'randomly' and assigned SEQUENCE numbers 'randomly' too. Several retries (delete images in Lightroom and install again) showed that the sequence was consistently random - ie the sequence was identical import after import irrespective of the sort sequence chosen. Using Total Commander I displayed the folder contents UNSORTED and discovered that Lightroom imports files in the 'native' directory sequence without regard to the sort sequence chosen or the time-date stamp of the image. This solves the time-lapse import conundrum which precipitated this deep dive into what was happening during imports.
Now if someone at Adobe could confirm this, it would be fantastic. It would also have avoided the collective energy spent by many users trying to decipher the 'faulty' process - from new batteries to cables to manipulating EXIF's etc etc
Yes, it appears that there is no documented import order for LR.
Is there a reason that you need to use the import sequence number instead of the original file number? The original file number will give you the correct ordering you are looking for.