Your views are enlightening. News about Italeri being the sole rightholder began to spread in 2016 if I recall correctly, under the centre-left government preceding the current day Lega-M5S administration. To my knowledge, but I can be wrong, there's no extant official document stating that the manufacturer holds the copyright on Italian air forces markings, past and present. I've just searched their web site in order to find out an explicit mention of that, but to no avail. A warning light of some interest to our question could be the logo present on some catalog's pages advertising and direct-selling aircraft kits with Italian decal options, such as the 1/32 TF-104G Starfighter:
https://www.italeri.com/en/prodotto/2738/1/1
The blue square on the right side of the page next to the box-art illustration brings the AMI emblem on the left while on the right the manufacturer qualifies himself as the product's distributor as well as "Official Aeronautica Militare (AMI) sub-licensee". To me, this sounds a trifle obscure; its meaning maybe relating to the fact that AMI buys stocks of Italeri kits on a regular basis to give them away as propaganda and public relations material. At the moment I ignore what other, different conjectures could be done.
On a final note, as you have already considered, it is doubtful that a such-termed TM , if any exist, would stand a court test if challenged since it is believable that Italian TM law matters have already been absorbed by EU higher-ranking legislation.