Yeah, it's a problematic model if we were to look at it as a solution to open source funding. It requires you to already be contributing heavily to a significant enough project that you'd be able to get these grants in the first place. Being able to get there without being paid along the way is a position of extreme privilege that not many have.
I spent a lot of time wrestling with the decision to even try this at all ("is it fair for me to do this when so many others can't?" and "will folks just think I'm abusing my position" are both things I had to come to terms with).
That said, if we do a better job of breaking down barriers to getting into that position in the first place, it's not a terrible model to start with. Getting a enough large grants to fully cover a salary from various companies a year is much more feasible than getting enough tens of thousands of individuals to contribute.
Working with these shorter sponsorships vs a full time employer also just feels more like the kind of open source work that got me wanting to do it full time. It lets me be much more flexible on when/what I work on (within reason, there are expectations on what "full time on crates.io/Rust" means). It's also helps to avoid situations where the employer is upset because you're spending time on a feature/bug/whatever that is important to the ecosystem but not directly useful to the company (e.g. working on a PG specific feature in Rails while employed by a company that uses MySQL)
