I'm just quoting from your quote of the passage at the State Department website. My interest in this thread started with the practical implications for “dual nationals” of which passport to use when traveling overseas. If you are a US citizen with dual nationality traveling overseas and want the assurance of whatever protection that is afforded you by the US embassy or consulate, my advice is to use your US passport. If you don't and then get into trouble in the foreign country, you may learn quickly (as my co-worker did) how little your dual nationality means to our State Department.
The State Department recommends the same thing. However, as a US citizen, the State Department must treat you the same even if you have dual citizenship. Problems arise when an individual with dual citizenship [and two passports] gets in trouble in the country of his other citizenship. Then, US officials have a difficult time invoking consular rights and privileges, including visitation in prison.
FYI: I worked for the State Department for 28 years.