From FB group Hobby Electronics
When a manufacturer purchases parts for the product they are making, they expect to receive what the engineers department had specified in the department’s documents.
When the parts are received, the Quality Control department is supposed to check to see if the parts received meet the engineering documents. I know QC can check for physical aspects, but they usually don’t have the expertise to determine electrical specifications. So it would be up to engineering to determine if parts are electronically suitable.
In the case of rechargeable batteries, the engineering might take some random samples and test them for capacity. After finding that an excessive amount do not meet specifications, the distributor might end up refunding or replacing the defective cells.
So the buyer should use suppliers that are reputable and are servicing industry. Then they can expect a better quality product.
Also there has to be an accurate measurement of capacity, so tests have to be done with a meter and procedure that is accepted by industry and by calibration laboratories.