No, a grandmaster can also consider moves way faster than an amateur. Watch Hikaru Nakamura solve chess puzzles [1]. He has already solved the puzzle and moved on to the next one before an amateur can even see the pieces on the board.
This is mind blowing. He solves these puzzles before I can find the king. How humbling. There probably aren't many instances like this where the gap between world-class and average person becomes as clear as in this video.
1940s to 1980s papers (the source of the claims) might think "amateur" means something different from people today. (they probably mean club chess players)