TS/SCI to DOD Secret - Reason reciprocity wouldn’t be granted?

If one has active TS SCI and is taking a position with DOD for a secret… is there a reason the individual would need an entirely new BI, fingerprints, and SF86? Confused.

I’ve read: https://news.clearancejobs.com/2016/11/06/scattered-castles-jpas-clearance-documents-stored/ , but seems the DOD FSO should be familiar with this type of scenario?

If you are in scope and no un adjudicated info it should work in reverse. I cross over from DoD all the time.

Thanks, asking for my spouse who has had an active TS SCI for an IC agency. After reading it looks a little complicated but would think they transfer would be pursued rather than the cost and time for an entire new investigation when he has a higher clearance.

Technically they all share info but I can tell you the three letter agencies all use their own system. So being visible in Scattered Castles does not make one visible in JPASS. It is stupid to repeat what was current and vetted. But bureaucracy reigns supreme.

According to this, you should be ok.
https://fas.org/sgp/othergov/intel/sead-7.pdf