The article also says, "Kornel said that the review showed that there is definitely some benefit from Botox for those with chronic migraine and chronic daily headache." The study compares relief from Botox vs. various daily preventative medications. For those of us who cannot tolerate or benefit from these medications, it provides tremendous relief that we can't get otherwise. This is something that your short review of the study does NOT discuss.
In my case, Botox has kept me from getting severe 24/7 migraines constantly. Now I get the severe migraines when the Botox wears off.
So the blanket statement that Botox shows little relief for migraines is misleading to say the least.