^No reason to "suspect" anyone. Foster was hired to write the novelization extremely late in the game. He had literally only weeks to write it. He didn't have time to expand on it too much. Actually he does fill in a lot; there's much more detailed discussion of events in the book than there is in the film. But he didn't have time to expand on everything.
One point in the interview that surprised me: when I asked Alan how long he had to write the book, he said "four weeks" but that that was normal for this sort of project... The impression I definitely got was that this didn't really differ from his Transformers or Terminator books in terms of time. The only difference - which actually probably *helped* the book - was that, very unusually, there was an actual finished film for him to watch before he started work on the novelisation. Normally there's not even a rough cut.