No it's not. Normally, WinSCP lists one folder, transfers the files, and then lists another folder, etc. With multiple connections, WinSCP needs a full list upfront. And then it does not list the folders again. So while it takes longer for the first transfer to start, the overall time of the whole operation is the same. Well, actually is shorter, as you are using multiple connections. So turning off multiple connection will definitely make the operation longer.