I tried to set to 0.5 (half rate) and it still does vanilla time
Half rate?
Did you grant the permission?
yes I did grant the permission
I just tested and it's working correctly for me.
It works if I set it to 0, it becomes instant. Can I not set it to 0.5 and it cuts the time in half? Are the only options 0 or 1?
It works just fine setting it to half. If it's not working you could have another plugin conflicting.