This means that it is impossible for them to make a patch or PR because it would conflict with the projects licence and fact its open source.

That’s not how it works. It just means the company owns the code for all intents and purposes, which also means that if they tell you that you can release it under a FOSS license / contribute to someone else’s project, you can absolutely do that (they effectively grant you the license to use “their” code that you wrote under a FOSS license somewhere else).