On Thursday, August 22, 2019 at 8:21:45 PM UTC-4, AMuzi wrote:

But for every web search 'internal wrenching bolt' I get Mil
Spec fasteners priced $15 t $30 each which are a magnitude
or more expensive than a cap screw, even a German cap screw.
The term seems to have special meaning.

The special meaning is that the manufacturer can bill the US DoD $30 for a bolt, when a $0.30 316SS hex cap screw will work just fine.