You mean the circle below the cameras? That is not a button, this phone has an active cooling system, yes you heard it right. The “button looking” thing is the fan’s protective grill, and the blue “ring” is the built-in RGB lights inside shinning through the gap for air to flow through. There is another set of openings on the side of the phone that gives another opening for air to flow through.
Because of active cooling this phone has no IP rating at all. Based on benchmarks and reviews I’ve seen so far they managed to allow the GPU to have nearly no thermal throttling, with the active cooling system. However, disappointingly, it does throttle the CPU a LOT still.
It’s actually not entirely that simple, there are a bit more nuance in this. They definitely do trade a bit of battery longevity, but sacrificing longevity alone won’t give you 100W on a battery that typically can only do 45W, you will get it bursting into flame instead.
Rather, many of those Chinese phones that charge at super high power were double-cell or multi-cell designs. A multi-cell battery would allow you to reach much higher charging current under the same voltage while generating less heat due to lower resistance between terminals. But multi-cell batteries are inherently less space efficient than single cell batteries.
So they took different priorities and also traded space efficiency for charging speed, and of course this trade also means they have to trade other things to get back the space for battery, such as size of speakers (and therefore speaker audio quality) for example.
On the other hand many of those Chinese phones also don’t abide by standard protocols even way before PPS became a thing, and many of them required their own vendor’s proprietary charger to get the marketed charging speed, which have a VERY non-standard voltage, so that they can keep current low by raising voltage higher than standard USB/PD voltages, to keep the power high. This often also meant you need not only the vendor’s proprietary charger, but also their proprietary cable too because their non-standard charging voltage is also beyond the voltage that’s standard for USB cables. This principle is common now with PD chargers (like for charging a laptop for example), but they have been doing this way before PD protocol, so they have their own choices of voltage/current combos that are incompatible with PD protocol. And of course those Chinese companies like Xiaomi and Huawei would never give a flying F about complying to established industry standards and avoid vendor lock-in, customer rights be damned lol