A phone advertising a high refresh rate does not run at that rate continuously. The display changes its update frequency many times a minute, and the reason is power rather than performance.
Refreshing costs power whether or not anything moves
Each screen refresh requires the display controller to read the frame buffer and drive every pixel, and that work happens regardless of whether the image changed.
Doubling the refresh rate roughly doubles this fixed cost. On a static screen the additional refreshes produce an identical picture at twice the energy expense.
Because displays are among the largest consumers of power in a phone, this is a substantial share of battery life spent on redrawing something that has not changed.
Variable rate panels solve it by dropping down
Displays capable of a wide refresh range can hold a low rate while content is static and rise only when something moves. Reading a page can run at a fraction of the peak rate.
The lower bound matters more than the upper one for battery life, since most screen time is spent looking at largely still content rather than scrolling continuously.
This is why two phones quoting the same maximum rate can differ noticeably in endurance. The minimum they can reach, and how aggressively they use it, differs.
The switch itself is visible to some people
Changing refresh rate alters how long each frame is displayed, and on some panels it also shifts brightness slightly because of how pixels are driven at different rates.
Most users never notice, but a minority perceive a flicker or brightness step at the transition, particularly at low brightness where dimming is achieved by pulsing the display.
Manufacturers reduce this by limiting how often the rate may change and by transitioning through intermediate steps rather than jumping.
Applications influence the rate they get
Systems decide the rate based on what is on screen, what the application requests, thermal state and battery level, so the same app can run differently across sessions.
Video is a common case where a lower rate is correct, because content recorded at a fixed frame rate gains nothing from being refreshed more often.
Perceived smoothness depends on consistency
An interface that delivers frames at a steady interval feels smoother than one that averages a higher rate with irregular gaps, because the eye detects the variation rather than the average.
This is why dropped frames during scrolling are more objectionable than a uniformly lower rate, and why stability is the harder engineering target.
The practical conclusion is that a peak refresh figure describes a capability, and the perceived quality depends on how consistently the system can actually sustain it.