I think they answer your question in the PSU section “Raspberry Pi 5 consumes significantly less power, and runs significantly cooler, than Raspberry Pi 4 when running an identical workload.”
That's not documentation of any reasonable level though.
An MPU designer expects to see something like "200mA draw from the 1.2V power-domain when running at 400 MHz" or "10mA draw from the 1.2V power-domain when in first level of sleep". (Maybe not this small since Rasp. Pi is a more powerful chip, but... you know... actual specifics).
"Will my Raspberry Pi 4 power supply work with Raspberry Pi 5?
"Raspberry Pi 5 is a higher-performance computer than Raspberry Pi 4, and you may have problems using an under-powered supply. We recommend a high-quality 5W 5A USB-C power supply, such as the new Raspberry Pi 27W USB-C Power Supply."
The question asks about power requirements, but the answer is about performance?
The first time I read that I thought the 5 needs more power than the 4, not less.
But then you get 5V 5A ... 27W that is clearly incorrect too. So my guess is nobody is proofreading the technical specifications, and everybody that cares was kept away from that page.
You don't specify a PSU by its energy consumption. You specify it by output.
Also, that 92% efficiency, is believable, but a bit high for a 5V 5A PSU (this is a difficult combination). I would expect any such unity to be marketed as high-efficiency.
If you frequently work it really hard, it'll have larger temperature swings and may fail earlier, but it'll still probably last quite awhile. The failure is not likely to be catching on fire.
An MPU designer expects to see something like "200mA draw from the 1.2V power-domain when running at 400 MHz" or "10mA draw from the 1.2V power-domain when in first level of sleep". (Maybe not this small since Rasp. Pi is a more powerful chip, but... you know... actual specifics).