Time signatures are not rewritten after they are deleted.
When you create a time signature after the first bar, then delete it, the time signature of bars subsequent to it are not changed.
1. Create a new score.
2. Create a time signature in the second bar that is different than the one at the beginning of the score.
3. Delete if from both staves.
4. Enter notes in any of the bars after where the time signature was. Notice that the amount of notes per bar (for all bars after where the 2nd time signature was) is dependent on the time signature that was already deleted, instead of the one which looks to be the correct time signature, at the beginning of the peice.
Also, it would seem that if you delete a time signature from one staff, it should be removed from all other staves too.