The CSR was correct if your friend does not hold a passport from Hong Kong (SAR China) or Macao (SAR China), assuming your friend is from the China. As noted, this information differs depending on what passport one holds.
According to Timatic, the source of this information for basically every airline:
Passport Information
U.S.A. (US)
2. Passports of all visitors must be valid for at least 6
months beyond the date of intended departure from the
U.S.A.
HOWEVER, exempt are:
- holders of visas type A1-2 or G1-4 (i.e. foreign
government officials or representatives to international
organizations), whose passports need only be valid at the
time of entry; and
- nationals of the countries listed below require a
passport valid at the time of entry and may be authorized
to stay until the expiry date of the passport:
a. Algeria, Antigua and Barbuda, Argentina, Australia,
Austria ("Reisepass" only), Bahamas, Bangladesh,
Barbados, Belgium, Bolivia, Bosnia Herzegovina, Brazil,
Bulgaria, Canada, Chile, China (People's Rep.) ONLY if
holding Hong Kong (SAR China) or Macao (SAR China)
passports, Colombia, Costa Rica, Cote d'Ivoire, Croatia,
Cuba, Cyprus, Czech Rep., Denmark, Dominica, Dominican
Republic, Ecuador, Egypt, El Salvador, Ethiopia, Finland,
France, Germany ("Reisepass" and/or "Kinderausweis"
only), Greece, Grenada, Guatemala, Guinea (Rep.), Guyana,
Hungary, Iceland, India, Ireland (Rep. of), Israel,
Italy, Jamaica, Japan, Jordan, Korea (Rep.), Kuwait,
Laos, Latvia, Lebanon, Liechtenstein, Luxembourg,
Madagascar Dem. Rep., Malaysia, Malta, Mauritius, Mexico,
Monaco, Netherlands, New Zealand, Nicaragua (see note 11
below), Nigeria, Norway, Oman, Pakistan, Panama,
Paraguay, Peru, Philippines, Poland, Portugal, Qatar,
Romania, Russian Fed., Senegal, Singapore, Slovak Rep.,
Slovenia, South Africa, Spain, Sri Lanka, St.
Kitts-Nevis, St. Lucia, St. Vincent and the Grenadines,
Sudan, Suriname, Sweden, Switzerland, Syria, Thailand,
Togo, Trinidad & Tobago, Tunisia, Turkey, United Arab
Emirates, United Kingdom, Uruguay, Venezuela and
Zimbabwe;
b. Chinese Taipei travel documents;
c. (provided being seamen):
Armenia, Azerbaijan, Belarus, Georgia, Kazakhstan,
Kyrgyzstan (not accepted are 1994 versions of passports,
which interior pages are red and with a single image of
the bearer on the bio-data page), Moldova (Rep. of),
Russian Fed., Tajikistan, Turkmenistan, Ukraine,
Uzbekistan;
d. holders of travel documents issued by the Governments of
the Trust Territory of the Pacific Islands.
**** NOTES REFERENCED ABOVE ****
*11However, Nicaraguan passports of any type, issued prior
to October 30, 1981 will NOT be accepted, even if holder
has a valid U.S. visa.