I'm not OP, but it's worth mentioning that Earnest starts to recoup its investment as soon as founders take a salary. Its calculator [0] shows a percentage of 30% by default - if that's accurate, for the 67%-80% of companies that fail, Earnest would still recoup 30% of its investment (ignoring other expenses and time value of money) even if those companies never saw a penny of revenue.
Also, they list a starting point of $2k-$5k in MRR, and on a $150k investment with a 30% split, they break even as soon as the founder(s) have taken $350k in total salary (again ignoring time value of money), including any salary paid out of the original $150k investment. I don't want to trivialize the process of scaling a startup beyond $2k-$5k of MRR, but I bet more than 20% of companies with $2k-$5k of MRR are capable of reaching that point.
[0] https://docs.google.com/spreadsheets/d/1h_L7oa3rbV8P-ZnMM-l1...
edited for clarity