the example here is 'De moins en moins de gens s'envoient des lettres'
But in the A2 lesson on de moins en moins /de plus en plus with adverbes and adjectives it says that you can't start a sentence in French with 'De plus en plus'
Why is one sentence right in one context but not in the other? Is there a difference between using de plus en plus and de moins en moins at the beginning of the sentence? Or is it because the rule of not using de plus en plus at the beginning of a sentence is only when using an adjective or adverb? And if the later is the case does it apply to de moins en moins also?