Automated download files from ftps server with multi thread

I am using WinSCP to download files from FTPS server automatically. What make me confused is that I configured 9 threads in WinSCP.ini, but when I run the script, there is ONLY 1 thread running. WinSCP Version: 5.13 OS: Windows 10 /7

WinSCP scripting does not support parallel transfers.

Though you can implement it on your own.
See https://winscp.net/eng/docs/library_example_parallel_transfers