Your reasoning is logical, but fails to pass the bar of "better than or even equal to just literally using some existing platform to attach a $X bounty to some issue I want resolved". There are several popular solutions that exist already to do that, your solution doesn't materially improve there, so what is the value add? It certainly gives the donor more confidence that the issue is being resolved in the way the donor wants it to, but if your problem is to make FOSS maintainer's life easier it doesn't move the needle in that direction, because it gives more power to already demanding FOSS users and less agency to the FOSS maintainer. And even if you solve that problem, does that value add cover a very-steep 20% platform fee?
I think it's a cool idea, don't get me wrong. But it has to be a very good solution to get adopted, like, it would have to significantly streamline the operations of getting bugs resolved by a FOSS maintainer, and I think it's going to be tough for you to try to beat "fire up my favorite agent in my terminal with an already optimized setup and give it this issue that has $X attached" rather than "I have perhaps inefficient token spend from a platform I have no control over and I have to take 20% less of a donation for that privilege"
In other words, I think you've built this solution for donors, and not FOSS maintainers, but really the bottleneck and problem and who you would be selling this solution to is not donors, but rather FOSS maintainers, and that's who you need to solve for if you want a platform like this to work. The donors have the easy job: they throw money at the problem to help it get solved faster. The FOSS maintainers have the hard job: They have to understand, accept the issue, propose a sensible solution, build it out, test it, etc. And your solution just makes it harder for those end users, because now they have two paths in their development workflow to getting issues resolved that they have to maintain, the non paid path and the paid path. So you're significantly increasing the overhead burden on these people and the material gain promised to those end users as the tradeoff is not convincing at all.