Benzos help with stuttering for the same reason alcohol does, they all bind the GABA receptor to turn down anxiety. The best medication I ever took was low-dose Zyprexa, a second generation anti psychotic sometimes used to treat Tourette’s. Very effective but I couldn’t tolerate the side effects. I’m surprised SSRIs are touted to help stuttering. Likely it helps with the performance anxiety. I say this because stuttering seems to revolve around an issue with a specific type of dopamine receptor dysfunction. Because antipsychotics decrease dopamine concentrations, a developmental Stutterer’s fluency improves.