I expect its more to do with being able to correlate the simulator to the real world. I imagine that PDLR was kept on by McLaren for so long as he was good at working with the engineers to ensure the simulator correctly replicated the real world. I expect its these skills they are after, rather than specific knowledge of the software.
Drivers differ in their ability to work as a development tool. Some are great at it and provide brilliant concise feedback that drives the team forward. Some are poor at it and struggle to translate their feelings and feedback into meaningful progression. Others just get sick whenever they drive the simulator
. Pedro has a reputation of being a good development driver, which is why I expect Ferrari want him.