This doesn't explain why they wouldn't accept the offer of work from /u/lopkeny12ko. I've been in the same situation multiple times. Sometimes I've been allowed to do the work and sometimes not. In the cases where I was allowed to do the work, I certainly took longer than they would have taken, but the work was complete much earlier (months) than they would have done it, the quality was just as high, and the other group didn't really have to put effort into it. It was actually a win-win for everyone and resulted in products actually shipping on time. On the other hand, the organizations that didn't allow this were all basically operational disasters. This sort of thing was just one red flag of many.
I'd recommend /u/lopkeny12ko to either stop caring and just put in minimal effort or find somewhere new to work. It doesn't sound to me like they're taking advantage of your skills.