In the beta i did not become human when I was a white phantom and I helped the host kill one of the bosses. when we won, I got about 4880 souls and a "Token of Fidelity." BTW the merchant at the start of the level sells a few Human Effigy also there is a few scattered around the map. Use them wisely.
^^ Correct. There may be other methods of gaining human form in the full game, but in the Online Test that is the only way.
Also, icancontribute mentions Tokens of Fidelity; that is one thing item I didn't mention in my guide. If you use them while you are a White Phantom (and possibly a Blue Phantom, needs confirming), you will heal the host player. Kind of like a reverse Estus Flask from Dark Souls, in a way.