I’ll actually make this a new post. I feel like this is the best answer (so far! Please comment more theories if you have them) to ‘how was the Not!Them both in the table and impersonating Sasha’.

It seems to me that the table limited the Not!Them by limiting its initial range of attack to ‘very close to the table’. However, once it took on a form, it could go anywhere. (I guess it couldn’t take a new form somewhere else with that form, but I don’t know. Probably not?)

Which means there was nothing in the table when Jon broke it and Michael’s calling Jon stupid for breaking some random table. Michael calling it effective binding is somewhat correct, as it did decrease the chances of someone getting impersonated, especially deep in Artifact Storage. It also meant that even if the Not!Them took on a human form, it still couldn’t escape into another form. Even breaking the Web Table wouldn’t allow this, because there wouldn’t be anything in the Web Table. (Of course, breaking it before it took a human form would do exactly what Jon thinks it did—release it.)

Binding the Not!Them made it so if the monster took a form, it would be stuck in it for the rest of the form’s life. Who knows what would happen when the form died? I guess it also explains why the Not!Them was still Not!Sasha even way after the table was broken.

This discussion brought up the problem of Graham and why the Not!Them took so long to attack him. Two theories, one not by me and one by me: first, the notebooks were somehow protecting him; second, having a budding Eye avatar protected him somewhat from the Stranger.