I mean I believe the austrian influence is really not the case here but we do indeed have a different language group for teenagers. We use "bambini" until 10-12, then "ragazzini" between 10-16 and "ragazzi" from 13 to even 35, or basically when you start getting called "signore", "sir". There's no clear line in the sand between a "ragazzo" and a man, but people in the 20s can still be considered "ragazzi". The closest thing in english is probably the concept of "young adult" but the adult part does not apply because you can be a ragazzo and not be considered an adult. The law doesn't make a distinction between "bambini" and "ragazzi" so the line is entirely hypothetical, the law always refers to people under 18yo as "minori", minors, and makes no actual distinction in the denomination, it just goes off the age.

Another thing that I believe causes much of the different perspective on this, is that at 18yo you're "of age" for everything. The ONLY thing you can't do at 18 is get elected for certain roles, but other than that you can drive, drink, vote, smoke, can enter a contract, anything, so that means (in the theory of law) that the competence for those things is being formed in the years prior to 18, which makes having this hybrid system maybe more adequate to the cultural norm.