And build them where, exactly? Could maybe be done in VSY, but depends on the size if it will fit as a lot of ferries are bigger than JSS, but huge difference if it's an aluminium hull, and their order book if full for the near future. Same reason the fast cat ferries were built overseas; there wasn't a Canadian yard that could build them, even if we wanted them to.
Build in Canada is a nice high level policy, but it does include exemptions for a reason, because sometimes just doesn't make sense.