Some of that could have just been where you were leaving your phone plugged in all day. A lot of the issues with degradation (and swelling) are heat management

Some of that could have just been where you were leaving your phone plugged in all day. A lot of the issues with degradation (and swelling) are heat management rather than charge management. Modern phones have no fans or cooling loops and make the assumption that they move enough through the air over time (even just sitting in people's pockets/purses/cases) that the heat they radiate isn't radiated back at them. Sitting on a hard, slow to cool surface such as an average table at all times of day, the phone's heat may have nowhere to go. It's useful to point this out in the context of EVs too: the EV batteries we've seen with the worst degradation had poor heat management (most model years of the Leaf up until recently, some early model years of Tesla's Model S); supercharging is an issue in battery degradation not just because of the rapid change in charge states but the rapid increase in heat released by the battery that has to be managed carefully (and away from the battery); EV batteries are expected to have longer lives and less degradation than phone batteries even of the same battery chemistry easily and simply because cars have the space for active heat management components (coolants, fans, heaters, etc) that phones have shaved in trade-off with more passive tools in order to maintain smaller pocket sizes.