[naz]

There are other Arab countries. Most people know what is meant by "Saudi" even if it's technically not correct

[coldtea]

It is technically correct, although not official.

Wikipedia: Saudis (Arabic: سعوديون‎ Suʿūdiyyūn) or Saudi Arabians are a nation composed mainly of Arab ethnic groups who are native to the Arabian Peninsula and live in the five historical Regions: Najd, Al-Hijaz, Asir, Tihama and Al-Ahsa;