To avoid these discussions about thermal inertia, it would have been better to log only end temperatures where the temperature is stabilized in time at a given input power.
Definition of thermal inertia: the degree of slowness with which the temperature of a body approaches that of its surroundings and which is dependent upon its absorptivity, its specific heat, its thermal conductivity, its dimensions, and other factors. Other factors - heat exchange with the environment.
In other words, thermal inertia characterizes the ability to resist changes in temperature over a certain time.
The heating time is practically independent of the heating power. But the final temperature depends on the heating power.