Yes, Spiralock only cover Metric and Unified threads but some of the UNC threads/inserts can be used in place of the Whit threads. As the male thread contacts at its tip, the flank angle difference does not come into play.
I introduced Spiralock threads into the final drive of a military tracked vehicle that I was designing.
it was shaking itself apart due to there being no way to use any type of locking nut as the fixed bolts of the epicyclic gear carrier were tapped into the carrier. Loctite did not do the trick, but the carrier was re-tapped and fitted with Spiralock inserts and the problem was solved. They really do work, but the fixing can be undone in the normal way, it is the vibration that they resist, not the steady torque when undoing.
Regards Richard