Isn't the problem for startups the lack of developers rather than the problem for developers a lack of startups? This seems to be aimed at the developers but in order to solve the startups' problems?
1) Applying to high-growth startups might be a numbers game or heavily network-based. Only some applications will have the opportunity to be looked at.
2) Not all developers have the "credentials" to pass the (flawed) CV screening process, until they land a particular role. However, much exceptional talent may have been rejected in the final stages of Big Tech firms, indicating their skillfulness, but they don't have the opportunity to highlight this.
Candidates that have obvious signals (example, worked at a fang) won't really need this service. But there are likely plenty of good candidates that get rejected at the resume review stage because their experience doesn't look that they can do the job even if the candidate is perfectly able.