Nit-pick print quality question - just curious

[printbus]

...The more I think about it, the more I think I'm seeing the stepper microsteps.

Unlikely. Assuming you have a 20 tooth pulley on the X and Y motors, the Marlin DEFAULT_AXIS_STEPS_PER_UNIT setting for X and Y should be 80 steps per mm. This means each microstep would give you 1/80 or 0.0125mm linear movement per microstep. Your 0.71mm pattern interval is in the neighborhood of 57 microsteps, again, depending on what you have for a belt pulley on the X and Y motors, and DEFAULT_AXIS_STEPS_PER_UNIT values in Marlin.

Anyone can jump in with different opinions, but I'm not aware of anything in Marlin that would cause it to pause at an interval like this.

BTW - if the issue is appearing on both X and Y, there could be an issue on the extruder that is affecting the ability of the extrusion to flow smoothly, and this could lead to a pattern like what you have. Perhaps trying another layer thickness or something else that would cause the extrusion volume per distance to change would confirm or rule that out. EDIT: Although having an extruder issue that causes the pattern to be consistent in the z-axis would be unusual.