Modern batteries should never swell, but will still wear out over time. Smarter battery management should be able to extend their lifespan.
It's the battery equivalent of the halting problem in software.
No manufacturing and design process is perfect, there will always be errors. If you do find a perfect design and manufacturing process, I think you wouldn't be posting here on hackers news but would be drinking champaign with Bill Gates and Warren Buffet.
Either way, you wouldn't use "should never" when it comes to batteries, which still has bulging, quality issues, etc throughout the entire technology industry with cell phones bulging, phones catching on fire, batteries on airplanes themselves being damaged, car batteries catching fire.
It's very well known that modern lithium ion battery tech isn't all that "failsafe" so using the words "should never bulge" in this context is very deceptive.
It is more likely that any battery using current battery tech in consumer devices will buldge within a certain number of charge cycles (which might be higher than the useful lifetime of the device), but it's very likely that the battery will bulge.
https://www.techradar.com/news/samsung-galaxy-note-7-battery...
https://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_...
https://en.wikipedia.org/wiki/Plug-in_electric_vehicle_fire_...
Unfortunately they still do.
Saw at least 2 Dell's and 2 macbook pro's with swollen batteries in the last 1-2 years, and this just in the colleagues in my immediate vicinity.
It's pretty scary when the touchpad starts to misbehave and you realize the whole macbook starts to bulge.