The extended warranty applies to higher-capacity 61Wh batteries only.
But I think, Framework’s new battery maintenance mode (where if your laptop is plugged in for a very long time, it starts charging the battery to less and less than 100%) applies to any capacity of a battery as it also applies to Laptop 16’s batteries. So to answer
Yes, they investigated this and released BIOS updates for Laptop 13 and 16 to prolong the life of all batteries when the laptop is plugged in all of the time.