Got bit by this.

random — Generate pseudo-random numbers — Python 3.12.2 documentation

• SAMPLE() (random.sample()) IS WITHOUT REPLACEMENT: no duplicates unless present in list (random.shuffle())
• CHOICES() (random.choices()) IS WITH REPLACEMENT: duplicates MAY happen.

Also:

• random.shuffle() works in-place. Sampling len(x) is a way to shuffle immutable lists.