That is because he is showing velocity as a function of the ratio of the hole diameters. The significant length in the Reynolds number is always on the top of the ratio, meaning as length increases, Re increases as do the influence of inertial vortex forces.

An important fundamental of Reynolds number is that it is a ratio of inertial vortex forces to viscous forces. Low numbers mean viscosity dominates and high numbers mean vorticity dominates....often referring to the tendency of a fluid to roll up into vorticies instead of staying smooth and laminar/viscous.

It takes a professor who really understands the subject to teach this appropriately in college/grad school so that the student gets a good handle on the fundamentals.

** looks like we were posting at the same time!