It's just a name. That's what happens when a three person startup where each person took one C level role grows a bit. A CTO at a 50 person company has fewer people under them than a middle manager at a big company.

um you mean direct reports? here

They probably mean the whole pyramid. Using the ten-is-a-lot metric for direct reports, as a middle manager in a large org I can pretty easily have 8 people report to me who each have 8 people report to them on average. So that’s already more people than the entire headcount of the 50 person company, and I’m only a 2nd tier manager, and may still have a half dozen roles between me and CTO (some of whom will have fewer directs, probably)

Could be skip levels in there if the organization is extremely hierarchical.