That achievement is likely to gather more accurate statistics due to the problems you mention. The Amid Evil devs can now confidently say that 12.7% of players who own the game have never started it. Meaning they can subtract that number from other achievement percentages to get a better idea of how many people are progressing certain ways.
The same is likely true for Minecraft’s inventory achievement, though that’s slightly less useful, as some players may make it a little further without opening the inventory and then stop forever.
Leaving the first planet in Stafield takes a little more effort, but not much. It’s safe to say that some of the 25% of players who haven’t done it haven’t ever opened the game. But that number will probably be close to 10%.