A car battery that lasted 300km new but now only 200km is still entirely adequate for a commuter with a 25km typical commute, and occasional 75km days out.
A degraded battery in these devices leads to things like random power-offs or dropping to 1% randomly (the display does not correct itself as it assumes it's safer to round down), particularly when it's cold. When it shuts itself down, it clearly displays that it has power remaining, but the device communicates that it thinks it knows better than you.
It is this bad software (and bad hardware) in these computing devices that ultimately what has led to EVs- new and especially used- being a tough sell far before the first one was ever released. The technology has proven fundamentally untrustworthy in low-stakes applications; why should it now be trusted in high-stakes applications?
(The answer so far has been "give them an utterly ridiculous horsepower figure", which did work, but it turns out normal cars can do that pretty easily too, and they're cheaper.)