Re. the jobs, companies are always hiring, because there's always turnover, and it's common to have the same job title and description for multiple people in a company. Also, it can take a really long time to hire in tech. There's really nothing odd about having the same job come up appear to come up repeatedly.
Re. the engine part, they can't ask for experience on a custom in-house engine, only on something similar.
As for the Sims 5 part... Pretty sure there's a whole lot of wishful thinking happening around that. While we know from Grant that there's something new in development, we also have been told repeatedly by Grant that Sims 4 is very far from done. I highly doubt that what he's working on is a successor game.
