The publishing of a list of ministers by the 5 Star Movement before the elections is an act of political propaganda. It is not an unlawful act, since there is no rule against it, but it has no meaning whatsoever from a legal standpoint.
The decision to do this shows the immaturity of this political formation, and its continued choice to not face up to the strict logic of our institutions. That is not a good omen for a party aspiring to form a government. This institutional infantilism prevents them from taking seriously the principles that our Constitution sets out for the formation of the government, and this naiveté is likely to have effects that are the very opposite of what they intend.
Many have pointed out, rightly, that this gesture runs roughshod over the prerogatives of the president of the republic, who has the exclusive authority to appoint the prime minister, and, upon his proposals, the individual ministers.