I still think that “lifeless rock” does not specify how lifeless - theoretically extinct or just lifeless enough to make human life either extinct or just miserable. I took it as the latter, and in that case even lesser cases than 75% of all species would suffice.
The first case, the theoretical and non-human focused pov is quite another thing. Like you said, there’s so many opportunities and adaptations for life to seap through the combs of doom :)
Maybe this is a beginning of someone’s mapping journey, so I wouldn’t be too harsh on it. If you’re interested in how the borders have changed throughout the history, you could also watch this https://www.youtube.com/watch?v=-6Wu0Q7x5D0