Different voltages for Single and Dual-supply (INA)
The front page of the datasheet is marketing information, not engineering. The reason for the specs being this way is most likely that somebody in the marketing department thought that there were customers who want +2.2 V operation, and customers who want +/- 1.35 V operation, but didn't think there were a significant number of customers who want +/- 1.1 V operation.
If you look in the Characteristics tables, you'll see that there are no specifications for the behavior of the part with a +2.2 V supply. Only for +/- 15 V and + 2.7 V.
If you're building 1 or 10 or 100 of a circuit, you might try operating it at 2.2 or +/- 1.1 V, and it's possible it will work. It's also possible it won't work, because they specify the part with Vref at 0 V, and it might not work with Vref only 1.1 V below the positive supply.
If you're building 1,000,000 circuits, you probably want to stick to operating the part according to the conditions in the Characteristics table.