good question Tim. Steep enough! Grade comparisons are something I'm hoping to write about. On this route, hardest sections were close to 3 (Spain), Diff (UK), II (UIAA), 8 (Aus/NZ) & 5.2 (US).
https://www.mountainproject.com/international-climbing-grades
My friends were quite happy with the exposure, 1 person took a safety rope on the hardest sections.
This grey area between the highest scrambling grades and easiest rock grades is fascinating stuff, where risk assessment and group capabilities come into play