Well we know that it is highly dangerous for psychotic people to reduce or stop their dose of antipsychotic drugs and one of the dangers of doing this is that it can cause suicide attempts and in some cases violent attacks on others or both
What difference is there between a patient choosing to lower or stop their dose or a professional. All such changes in drug doses of these powerful and necessary drugs should be closely monitored for that reasons alone.
The danger is reducing it to a level that is ineffective. So they reduce it slowly and monitor to make sure that it is not reduced to a level that is not working anymore.
At the time of the murders they had no idea that anything above 100MG was essentially worthless.
Today Ferguson would not have started her out at 200MG he would have started her at 50-100 and after some time would try seeing if a 20% reduction from that point lost effectiveness or not to try to ascertain the minimum amount needed to keep her from relapsing.
Keeping someone on doasges above 100MG is not considered safe and was reduced because of the problems it and the countering agent were causing her. She was doing better after the reduction than before and the reduction was to the optimal efficacy level.
The most simplistic explanation of schizophrenia is that it caused by overactivity of dopamine in the brain. Haloperidol blocks the receptors that dopamine act upon thus preventing overactivity of dopamine in the brain. This is how it keeps psychotic illness at bay.
The goal is to find the minimum level of Haloperidol necessary to block the overactivity. It must be monitored because if you go too low then you will find it is not working and then realizeneed to go back up to the previous level. That is how you determine the ideal amount.
Since 200 MG doesn't prevent more activity than 100MG it is not really of any value so far as controlling the illness and dropping form 200G to 100MG is not going to suddenly enable overactivity to take place again.
If there is going to be withdrawal issues they would surface shortly after the time of the reduction not 3 weeks later. Haloperidol controls aggression and agitation. 100MG does so quite well. If she were going to become aggressive because of withdrawal it would not have waited until 3 weeks later for such to surface. It would not be likely anyway since 100MG is the optimal efficacy dosage.