I stand corrected. So what happen if a major bug is found late in the process ? I suppose either the feature is dropped for this release or the release delayed until the bug is fixed and the feature is kept. Do you know which is it ?

There isn't a hard policy; it'd be a case-by-case decision. If there wasn't rough consensus, it'd be up to the release manager and technical board to decide. So far, this hasn't really happened: there have been a few bugs that have delayed releases by, like, a few days or a week, but nothing so severe that has seemed to warrant pulling a feature down.