Too many "nodes" (which translate into short linear motions on the machine) can definitely slow up a machine, whether it has a "modern" control or not. Every control has what is known as a "loop cycle" time. This is a loop that the control runs. The loop contains things like "has the operator pressed the e stop?", "has a limit switch been tripped?" etc, etc. The list is actually quite long. It takes X milliseconds to run the loop. If the machine motion is so short that it takes fewer milliseconds to read the commanded destination, then the machine does exactly nothing in terms of motion. To combat this, look ahead buffers are created. But if the motion is really sort, those buffers get emptied and the machine starts to slow down.
You can play around to cause the effect even with a straight line. I once did it with an industrial controller. Programmed .0002 moves in a straight line. Tens of thousands of them. Sure enough, things ran nice and smooth right up until the buffers empted. Then, slowwwww and chattering.
Low Profile CNC Router Vise