No, but you have to properly safeguard the data in transit AND at rest, and the black magic fuckery would be in allowing folks to access that data via an unsanitized and non-standard endpoint, while still accounting for possible counterintelligence shenanigans. That's a different problem to solve than tunnelling an air-gapped network over public pipes.Once the SIPR trons go through whatever magic box is at the end of the metal pipe in the squadron spaces they still end up on the rest of the internet. It's not like they laid SIPR fiber all over the country.
I have some ideas of what said black magic fuckery could be, but I'll refrain from speculating in public.