Squatting associated with laying hens and point-of-lay pullets occurs when they sense something hovering over them. If these pullets were off all by themselves with no rooster around and you weren't coming up behind them, then their squatting may not be associated with getting ready to lay.
If these pullets were outdoors under an open sky, it's possible they caught a glimpse of a hawk and it scared them. Squatting is a reflex action to anything approaching from above or behind, and I've seen my own hens freeze in panic when they spot a hawk swooping down at them. It's occurred literally right in front of my eyes. Luckily, that time the hawk came up empty.
If you walk up behind your pullet and just touch her back lightly and she squats, then you can expect the first egg in less than a week.