Ciao @Nicola Mathias 46 and welcome to our community.
In terms of your question about "eligible" — I think what they mean there is that they aren't eligible because they're in the mandatory waiting period between dose one and dose two. In fact, in Italy the vaccination certificate (and thus the super green pass) becomes valid on the 15th day after the first dose, but is only valid until the date of the second dose, in order to provide coverage during this "bridge" period between the first and second dose. However, it's different in different EU countries. Some don't activate validity for the EU Digital Covid Certificate until both doses are completed, and sometimes the wait period is 14 days following the second dose, not the first as in Italy.
Have you been following the similar discussions taking place in our UK Travellers group92? I'm going to add you there; have a look at the threads and feel free to interact with others in that group who have a lot of combined knowledge after weeks of trying to sort out these confusing regulations. Also, have a look at this post: Everything we know about a super green pass for minors with one vaccination dose137.