Anyone in the industry could have a bug get through testing. Some companies could have a severe and readily reproducible bug get through testing. A few of tho

Anyone in the industry could have a bug get through testing. Some companies could have a severe and readily reproducible bug get through testing. A few of those companies have a hand-rolled update mechanism, and can accidentally break their ability to roll back a bad release. A few of those companies are in a position to push a release that breaks not only their own software, but the entire OS. Very few companies in that position would roll out to 100% of client machines in a single worldwide deployment.