They do not all weigh the same, even if the spine is held constant. Yes, 23/64" are heavier, on average, than 11/32". But the weight of each individual arrow shaft can vary greatly.
The last dozen arrows I bought without first weighing them myself had a difference of 138 grains from heaviest to lightest! That's the last time I do that.
We sell POC shafts. We spine and weigh every single shaft ourselves, and then put them in groups. Typically spine groups are within 1#, and grain weights are within 10gr. Often the sets are better than that. Give me a call or shoot me an Email if you are interested in cedar and I'll let you know what I have on hand.