In majority of the cases scripting is used to automate unattended file transfer or synchronization. For that reason majority of the scripts should start with command option batch on (or abort) that makes the script abort on any error or prompt, which would otherwise result in an interactive prompt that stalls the execution.

If you open the scripting session by providing session URL on command-line, it starts opening yet before the option batch on applies. So errors and prompts during the opening of the session may stall the execution of the script indefinitelly.

Hence preferred approach to use open command after using option batch on.