Indeed, that is UA's policy. Sometimes when coming west from the east coast, I will bring 5-7 dozen fresh bagels, and if I do not have a duffel bag, I'll put them in a box. Almost every time (ironically, except two weeks ago), I had to sign the waiver. Typically, I'll get asked what the contents are and sometimes I'll get some good responses, especially since the smell is powerful from fresh bagels!

Next time, buy a cheapo bag if you are concerned about the contents.