That site is great
If they speak to the vet there is lots of alternatives. Personally I found the Hill's made Scully's diabetes worse and we now use Innova Evo (with regular vet checks) without any problems and so far he doesn't need insulin shots. Innova however is close to the same price!
Lots of people have found that wellness canned is good for diabetic cats - but it involves a lot of trying the food for a while and measuring the blood glucose a few times a day to check which foods agree and which ones don't with each particular cat.