I have no idea about SF's processes specifically but it's certainly not universal practice to have conference presentations signed off by PR or anyone else within an organization. Doesn't mean there can't be repercussions if you say something inappropriate or disclose information you shouldn't, but not all companies require signoff from presentations.
Any comparatively large corporation very likely has a release process for these sorts of things where a bunch of groups (like PR, maybe Legal etc) would take a look. Releasing company IP as open source outside of such a process would be a gross violation of any number of non-disclosure agreements between employer and employee.
