Currently, Rectangles with zero-width and zero-height are ignored for autoscaling purposes, but not other zero-sized patches:

from matplotlib import patches, pyplot as plt

ax = plt.figure().add_subplot()
ax.add_patch(patches.Rectangle((-5, -5), 0, 0))  # zero-sized at (-5, -5)
ax.add_patch(patches.Circle((5, 5), 0))  # zero-radius at (5, 5)
ax.relim()
ax.autoscale_view()
plt.show()

results in axes autoscaled around (5, 5) (so they include the circle, but not the rectangle). I would argue that Rectangles should never be ignored, even if they have zero-width and zero-height, both for consistency with other patches, and because such Rectangles are likely not drawn with no reason.

This behavior (implemented in Axes._update_patch_limits) was introduced in f24d06c to support log-scaled histograms with empty bins, but is not necessary anymore as hist autoscaling was fully reworked in #14581, making this behavior unnecessary (the check in _update_patch_limits can be deleted with no bad effects); perhaps it was even already unnecessary before though.

Also, note that #2942 already weakened the original patch by going from ignoring Rectangles with zero width OR height to only ignoring Rectangles with zero width and height.