GJ, for most cooks that’s not a particularly significant issue in an oven, particularly when empty. The issue is Anova uses rapid temperature monitoring while most manufacturers don’t.
A variation of only a few degrees is superb performance considering how thermostats work. Opening the oven door during operation will cause larger temperature variations.
There will always be residual heat in the oven’s elements after the thermostat interrupts their power which will raise the oven cavity’s temperature above its set point. The typical domestic oven will often have 25-degree or greater temperature swings but they won’t be revealed by a slow thermometer.
Some high end ovens have calibration adjustment features that can reduce temperature variations but i wouldn’t expect it at the Anova oven’s price.