I have seen this before and I believe you are in error in its interpretation. The rim and the circumfurance of the vessel itself are not necessarily the same. For example, my tea cup might measure 3 inches around but while its rim measures 3.14 inches in diameter.
Seeing that the text descibes a rim and seeing that the vessel was designed to bath in a rim wider than the main vessel makes perfect sense.
Did M.C. Escher design your teacup?
Seeing that the text descibes a rim and seeing that the vessel was designed to bath in a rim wider than the main vessel makes perfect sense.
And it does, too, but then it would take a distance larger than pi times the diameter to measure around it, not smaller.