Desktop use is also very uneven, leading to a lot of large changes in temperature (35 -> 80 and back), which causes more material stress, than when everything is loaded evenly all the time. The same is true for electrical transients.

If you have a good cooler with lots of thermal capacity and good fan (like an Arctic Cooling or Noctua, nothing at the extreme end), the increase is very gradual. Also, short spikes in loads are well absorbed with minimal temperature changes.

Nevertheless the numbers you mention are neither unrealistic, nor impossible in stock cooling and/or sustained load scenarios.

5950X with the top of the line noctua cooler jumps from 35C to 80C very quickly when a single core is loaded at 100% (this is the worst case, because it leads to max voltage being applied to the CPU cores (because of boost to almost 5GHz), compared to loading all 16 cores at 100%, which will result in just 60˚C temperature sustained over long periods of full load). So interestingly, compiling the Linux kernel with 32 threads is less thermally straining on the CPU than browsing the web and a single page loading 10 different animated ads.

This mirrors my experience with Zen 2 and 3 as well. Multi-core loads result in just a few W per core and decent temperatures, while few or single core loads push per-core power into the 12-16 W region and the temperature rise/fall is basically instant (brick-wall at 10 Hz update rate, though it's unclear what filtering is applied and how the CPU derives a single temperature from its probably numerous sensors), which suggests that they're not limited by the cooler, but rather by the thermal impedance from the active area to the cooler. The core itself is really tiny (iirc around 4 mm²)...