Heres my 2 cents on tires in general

Tire manufacturing isnt rocket science. Yes most companies take pride in their product, but when your dealing with raw materials and end products that have elasticity your not exactly going to have 2 tires (batches) that are exactly the same. Quality control is often alot more qualitative than quantitative to boot. It is more cost effective to send replacement tires to the minority than remake and entire batch of tires. Same thing with rims. I can't even find 2 rim strips that are the same. Also its not a "this company is small and this comapny is large" type of thing, it has more to do with the model or batch. ITs like saying all Nike shoes are smaller than other brands. Not true.

On a side note temperature can effect tire pressure a great deal. This is probably not the case here but its worth mentioning for everyones wealth of knowledge. If you leave you high pressure tires out in the sun, your tubes can explode. I always have to be sure to underinflate peoples tubes in the summers otherwise my shop does alot of free replacments!