chiller primary secondary pumping system

Hi everybody

I have a question on primary secondary pumping system. I know that the benefit of this system is based on variable speed secondary system to manage the variable flow rate in secondary loop based on cooling demand. but if due to some limitation we use constant speed secondary pump is there any advantage relative to constant speed primary only system(only having one set of pump)?
I think it is two set of pumps working in series and also we do not need decoupler pipe too.
Am i right?

thanks

any answer for this?