First of all, the argument by the inspector is his or her view, an opinion...secondly the argument does not encompass low speed piling or differentiate between the high speed piling such as vehicle mounted testing drills.
Large piling on major construction has revolutions at or between 20-53 ps, not exactly the quickest turning, churning out bores 200mm diam upwards ( approx). with fully trained and competent crews.
There must be some difference in the identification, and I cant see guarding working on the big rigs, other than simple assessed systems.such as operating warning lamps, easily identifiable, or a curtain
On smaller faster rpm rigs, then yes, guarding is a must , not defeatable and interlocked allowing the machine to come to a full stop when opened.
Regards