many people are patriots of their countries. if state agency would approach them proposing to have paid OSS work and help their country to fight terrorism/dictatorships/capitalists/whatever-they-believe, they will feel like killing two birds with one job
While this seems plausible, it is notable that this person seems to be anonymous from the get go. Most open source maintainers are proud of their work and maintain publicly available personas.
While I don't doubt there are people who would gladly do this work for money/patriotism/whatever, adding a backdoor to your own project isn't really reconcilable with the motivations behind wanting to do OSS work.