Yes, this proves that keeping laptop on charger is killing battery for sure. It is a device designed to be used mostly on batteries and recharged. Maybe better to invest in Mac mini when you plan keeping it connected 100%?
There is other thread in this forum with guy fighting load cycles for profit of inflating resale value of used MacBook 😂😂.
Actually when considering to buy used, I will stay away from these +3 years old MacBooks with original battery cycles <100 - battery is ruined on those.
That is 100% true, from my experience, a 'high' or 'normal' battery cycle count is better than low when it comes to 2+ year old MacBooks. This typically indicates normal MacBook usage vs running it closed and always plugged in.
Many MacBook that have <50 battery cycle count after several years are more prone to issues based on my first hand experience.