Preloading the DOCX skill hides a cost real runs pay. In the harness I use a skill is listed as a name plus one line, and the body only loads when invoked, so the 10-call skill baseline probably undercounts by a step.
Yep, a real run with DOCX skill would pay an extra tool call (e.g load_skill). We pre-loaded its context because we wanted to neutralize setup differences between tools and just focus on editing.