Don't worry at all, one of my friend also had almost none travel history , but was told to submit schedule A. He received portal email within 2 months (single applicant) .My background check is processing from the beginning.
I am not sure why they asked me to submit Schedule A form. I didn't have any rejections or any issues in the past. I submitted the form with the same info as application.
My travel history for last 10 yrs was already declared in the application. [It was only 15 days travel history]
It is really freaking me out.
Sometimes they do ask to resubmit maybe just for cross- verify. So its all good.