While the Pixel 6 ushered in three years of major Android OS version updates and an additional two for security patches, that’s still nowhere near the longevity of the iPhone. Google hopes to change that on the Pixel 8 and 8 Pro with noticeably more OS updates.
It will never overcharge either way, that’s handled by the battery management system inside, charging naturally slows towards the end as it enters CV charging state due to the internal resistance of the battery. It’s just that charging over about 80% puts a lot more wear on the battery.