I worked for a software consulting company in Japan, we had a contract with a big well known company. The contract gave a precise date for the delivery with huge fines if we delivered late but there was also a long bug fixing period after the initial delivery.

So we had overtime for 2 months working from 10am to 4am just so that we could deliver the "feature complete" software. If any bugs were found they were classified as either blockers (feature cannot be shown without) or scheduled to be fixed after delivery.

My boss knew it was stupid, he didn't like it but it was the standard contract from that big Japanese company and we were small and they weren't going to change that.

That's a very narrow viewpoint. From the customer perspective, defect rate is only one component of the product quality vector.