Seller insists it will be fine.

I'm sure it will be fine. My figs were shipped in similar conditions and some even had fig leaf rust. They had transplant shock and lost all of their leaves. But they quickly grew back. This was in May though. Not sure what zone you are in but in a lot of areas this is the time of year figs will go into dormancy. You could be better off potting them up properly and letting them go dormant naturally. Others will know better than I.

I am in growing zone 6

Tips still look green and that is all that matters. Transplant shock and/or went dormant. Keep warm, indoors, and if you want lightly use a liquid fertilizer. May take a bit buy you should see growth soon. Don't expect any figs till next year.

IMHO, that is a rooting done for profit and not care.