They are not supposed to... They were ''lucky''... or they are simply going to delay the cessation procedure when they apply the citizenship application form (Travel history is checked systematically, in particular to check the eligibility period of residence... and it is often at this point that they notice it)... Do not play with fire, to come and cry afterwards, you have been warned...
The cases of judgment with cessation due to the use of the travel document of the country of origin exist, it is not imaginary, several cases exist.
Have you ever heard of Murphy's Law? ... Life is hard, and it will happen to you without the others (or the others it will happen to them later as I explained) ... Everyone knows the rules... Now you are an adult: Do this whatever you want... but be prepared to accept the consequences.