All seats pass testing withOUT using the top tether. They also must pass a more strict test where they CAN use a top tether to help which is why using a top tether is always recommended. I can only think of a few seats that actually
require using the top tether (Frontier85
after 65 lbs, Safeguard Go/Safety 1st Go Hybrid, and Ride Safer Travel Vest when using a lap only belt).
That said, most car seat companies don't release crash test results, but Diono (formerly Sunshine Kids) does, and the Radian passes the more strict test
without the tether. I've heard the Graco Nautilus does too, but I don't believe their crash test results have actually been released to the public for confirmation of that. It's quite possible other seats do as well, but we just don't have access to that information.
Also, in echoing the PP, if the Pathfinder is a mid year 2001 or newer it DOES have tether anchors. If it's an early 2001 or older, tether anchors can be retrofit if your friend would be willing. The part kit should be relatively inexpensive (~$15).
ETA: I'm really slow, lol!