I can read Dutch but maybe you can post the URL where you found this?

https://www.trenitalia.com/it/altri_treni/regolamento_interrail.html

OK, that checks out. Apparently, The Frecciarossa 4L has 4 "service levels” and only 2 of them are accessible to pass holders. It also looks like 2nd class pass holders cannot buy an upgrade to 1st class, which is also confirmed by Belgian railways (NL/FR).

Frecciarossa classes:

Standard - 2nd class

Premium - 2nd class with better seats and free snack and drink

Business - 1st class with 2+1 seats and free snack and drink

Executive - luxury class with included meals (only on longer journeys) 

Frecciargento classes: only for ETR700 ex Fyra

Standard - 2nd class

Premium - 2nd class with better seats and free snack and drink

Business - 1st class with 2+1 seats and free snack and drink

all other trains of Frecciargento, Frecciabianca, Intercity and Eurocity

2nd class 

1st class (2+1 seating), in Frecciargento with free snack and drink

So it apparently means that those passholders=cheapgoats cannot get the free snek/drink that those bisnesmenny get and pay extra higher fare for. UNderstandably. It also seems you even cannot get it by paying for the upgrade to it, which would be permitted with normal tickets.

Its is nothing new for passholders; DB in DE also bans the use of its glitzy lounges to passholders 1st cl.

But on the other hand in the Uk (very best value!) and AT/OeBB you can enter those lounges (or at least could when I had a 1st cl. pass 2-3 yrs ago), and in GB even with free ´meals´ (well, it was more as a snack) during the ride on some IC-trains. But perhaps they have now also been scrapped as yet another economy-measure.