The email and phone service for people contacting the UKV&I from overseas
does seem to be outsourced.
Not sure if it is the same helpline for people calling from within the UK, but there is no reason to suggest otherwise, based on the quality of information.
The reason to submit biometrics for the citizenship applications is that before 2015, the biometric data held by the Home office throughout the immigration process had to be destroyed when you became a citizen.
Subsequently, the government would only get your biometric data when you applied for your passport. If you did not apply for your passport (by having a CoE-RoA in a foreign passport, for example or just forgoing a British passport), the government could not capture biometric data.
In response, the Immigration Act 2014 made specific provision for biometric data to be captured during the citizenship process. Such biometric data, subject to rules, is destroyed either when a British passport is acquired (which requires you to submit a fresh set of biometrics, ah-hah) or at the end of 10 years.
Further reading:
The British Nationality (General) (Amendment) Regulations 2015
I am not a lawyer or immigration advisor. My statements/comments do not constitute legal advice. E&OE. Please do not PM me for advice.