Why would Broadcom extend an offer to someone only to fire them on November 4? That makes no sense. Broadcom committed to taking a certain number of people. If Broadcom later decided they didn’t want some of those people, they simply would not have extended an offer to them. These people would have been RIF’d by Symantec and Broadcom would have been responsible for paying Symantec for the severance costs.
This may not be true in countries outside the US because of local labor laws, but it is definitely the case in the US.