Now that you mention it, that was also what our burndown charts looked like (unaffacted). Our Scrum Master did use a factor of "actual hours worked vs. planned

Now that you mention it, that was also what our burndown charts looked like (unaffacted). Our Scrum Master did use a factor of "actual hours worked vs. planned hours worked" to determine how accurate our SP totals per sprint were. I.e. if we did 100SP in Sprint 1 with no overtime, then 100SP in Sprint 2 with 20h of overtime, we underestimate the SP in Sprint 2. I am generally not a fan of time tracking (especially not down to minute accuracy or per-story), but I see sth. like "8.7 hours worked on Tuesday" as a useful but not misleading measure.