New Bottom End Balancing??

Hi there.
Took my bike into the shop the other week to get checked out and was told will need a new bottom end however they told me it'll take a while to arrive then once it does, they'll have to send the conrod away for balancing or something. Im just wondering out of curiosity, why it actually needs to be balanced? ive heard of refurbished conrod's being balanced...but never heard of brand new bottom end's needing to be balanced??

yeah that's what i thought. thanks for that mate. ill give em a call tomorrow and see what the go is.