But all the trains between Milano Centrale and Torino Porta Nuova (note both words end in an "a" not an "o") are high speed Frecciarossa trains taking one hour. All Frecciarossa - all Freccia and IC trains in Italy in fact - are all reserved only. I would say you get grace period. You just have an opportunity if - as Dario says - you have purchased full priced tickets in advance. But also, as he says, nobody does that.
If you take advantage of the much lower prices you can get buy buying ahead those discounted tickets go poof if you miss the train.
Regionals don't care if you oversleep (at least not more than 4 hours) but those prices never change and are the same price in person or on line - and those real tickets need putting in the validator and stamping before you board or there is the very real likelihood of a large fine to be paid on the spot.
So, no grace period - some lighter conditions if you paid full price for the fast trains.