The packages are issued so early because HR wants to get rid of the employees that's been identified as "unfit" ASAP so they can close the books on them ASAP. They are also banking on the fact that most victims will not negotiate the package, accept the terms as is and signed off on them.
As for the internal postings, it is a big sham that offers false hopes to the individuals that are already in a very stressful situation. The number of postings is very limited and only small number of individuals are qualified for the positions. It takes a long time to process the applicants - do you really think that they can choose the best candidate within 3-4 weeks? HR will make the others wait till the 11th hour then tell them that they will not be considered and get ready to exit (another kick while you are down already). This is how the dirty game is played out at SAP.
Please make sure you review the package in detail before you sign, ask for advice from an expert if you are not sure because you only get one shot at this. Good luck to you all!!