Spoilers Picard Movie & TV collection Blu Ray: A Rant

[Noname Given]

The difference with someone being assimilated and Hugh was that Hugh was already a member of the collective.
When someone is assimilated there must be some way to prevent their individuality from spreading into the collective. With Hugh there was no need for "individuality eraser" as he was already a Borg. That's when Picard's plan works. Hugh would be plugged back in and Picard's plan would work.

They also would need to have a way to keep it from reasserting itself if the Borg drone was damaged in some way or something glitched.