"Invented". Yeah
It's been a known fact for over ten years. You can find a few papers out there. Basically the max number of charge cycles of a LiPo/Li-ion battery decreases as the max battery voltage increases.
The voltage at ~80% SoC (I think something around 3.92V for the average battery) is often considered a good compromise between the gained battery life and the lost capacity. Another benefit for the user is a reduced charge time.
You will also notice that the phones will be getting bigger and bigger to accomodate larger batteries to make up for that.
One thing to note is that the battery voltage *while* it is charging is not that good an indicator of the SoC. The open-circuit voltage is a better indicator AFAIK. This is not a problem when fully charging the battery, as the normal charge cycle is made of a constant-current, then constant-voltage at 4.2V and the end-of-charge is detected when the charge current in constant-voltage mode drops below a few % of C. If you're only charging it up to ~80%, you usually won't be in constant-voltage mode and estimating the SoC in that condition is much less accurate IMO. Of course a given device manufacturer can calibrate/model the battery in said device so they can be not too far off. Just saying though that if fully charging the battery, its OCV will indeed be pretty close to 4.2V, whereas if charging it only partially, thus reaching a lower voltage, once the charging is stopped, its OCV after just a couple seconds to a couple minutes can drop significantly, so IMO a decent model is definitely required to do this reliably if you really want to get a 80% SoC.