Calculating SMD resistor temperature rise
Probably the 100% power table illustrates the maximum point surface temperature rise of the resistor, likely the center of the top surface, such as you would measure with an IR camera. This is the "hot spot" temperature and is of interest because it could cause damage to wire insulation etc. 

Panasonic (for some parts) specifies measuring the temperature of the hottest of the two terminals, and derating based on that.  See this: