Devil's advocate time here:

Why waive the multi requirement for SE fighter types but not for those who have a whole bunch of SE turboprop time, like in a TBM/Pilatus/Caravan?

If the purpose is safely delivering airline passengers and/or cargo to their destination, and regulators WANT a significant amount of multi-engine experience for safety, then experience in one SE turbine (pointy nose) should be just as good as another (prop nose).