Just noticed this - Threads were made in body, then body converted to component. After that some more threads were added, and the component derived into a new design. After derive the threads made when it was still a body are not included in the derived component, but those made after it became a component are.
Can't share this design due to sensitivity, but here's the original design file, threads on left created before conversion to component, those on right added after:
And after deriving to new design:
Blue holes have no threads, red ones do. I'll have a play later if I get time and see if I can repeat this behaviour.
