Radiant: Why is the speed grade showing that it is using a timing model at 1.0V and not lowest specified supply voltage which is 0.95V?

Radiant: Why is the speed grade showing that it is using a timing model at 1.0V and not lowest specified supply voltage which is 0.95V?

The 1.0 V specified on the speed grade 8_High-Performance_1.0V is just the name of the speed grade. By default, the voltage used for the setup analysis corner is 0.95 V. You can see this on the Device Constraints Editor (DCE) --> Global Tab --> Voltage (V) field.
Default values are shown in purple color and the default value for the Voltage (V) is 0.95.