I believe this model is quite old (at least in some form) so there have been opportunities to review it. I confess I haven't looked, but I haven't heard any defects have actually been identified. If the model stood up to peer review I assume the results it produces are at least consistent with the expectations of the people who wrote the mathematical model.

Hopefully this will be a watershed moment that makes it easier to cost a research software engineer onto a grant in the future.