Maybe they didn't know everyone left the stardrive section.
The warp core is gonna blow up, gotta evacuate, gotta detach the saucer and get away in minutes--with or without knowing everyone has left the stardrive section, even without an "ALL CLEAR".
Given the critical circumstances, they'd have to cut and run even if some persons were still left in the stardrive section.
If you listen to the Braga/Moore DVD Commentary, they state that the teddy bear the little girl Geordi is carrying drops, is a sentient life-form that is killed when the star-drive section detonates.
Poor Teddy Bear... along with Ballsack the Lizard Dog from TSFS, it is a Trek tragedy.