lol, my VAIO Z Canvas, a very expensive tablet at the time(still made in China though), has a swelled battery after about 2 years of use(almost plugged in all the time), in fact I now suspect that it started to swell less than a year after I bought it, because there was an anomaly with the touchscreen and the digitizer layers at the time, but then that spontaneously resolved, until recently when I discovered increasingly irregular backlight distribution and finally noticed that the screen isn't flat anymore and has already partially lifted off of its glue seal around the edge of the aluminum chassis. Unless there's some other source that would explain the internal stress(it's been sitting on a desk during most of the development of this issue) it's a swollen battery.
I'll still need to use it while I consider a suitable Surface model. Whatever I buy I need 16GB of RAM which would make a hefty premium, and the Surface models don't have as many ports either, I'm also not a fan of having to separately buy a keyboard (that also doesn't work detached) and how the integrated stand doesn't deploy in a way that allows a comfortable portrait view.

Well that's a 3-year old phone. I'm not saying the batteries shouldn't last more (I've always been a hater of non-removable batteries), but for 3 years, a lot of "premium" phones would suffer the same fate.

Do I see a removable battery with an open back in a phone? Because if so, then mission accomplished.
Batteries expand and explode all the time. So what, who cares? The cheap Chinese phone got what truly matters.

We're merely cataloging our recent experience with a particular device, not demanding any manufacturer action

That is meaningless from a statistic point of view.
Samsung, which is a global smartphone builder, had exploding batteries in its one grand phones. That is what I call a news. But a battery getting inflated in one (I say it twice, in your sample), it is irrelevant.