retrenchment

our company declared retrenchment due to a loss of project that will result to a huge company loss. all of the employees under that project were retrenched. one month notice were given and .5 per year of service were given as severance pay.
it was advised that the project will end on dec 15. so all employess must still report to work until such date.
The problem is this. Dec 1 when the company sent notice to a few people. around 8% of the total nimber of people retrenched. they are still working on the project from dec 1 to dec 15.
majority of the people, 92%, had their notice received on dec 15. inside the 30 day period, they don't need to work or report to the office.
The question is, is there any basis for the 8% to ask for the payment of the half month they worked for? all of the employee's project end is dec 15th so why do the company had to choose a few people to send immediate notice when majority of them have a different treatment.
we believe that since this is retrenchment, all of the people who were involved will be treated equally.

Maybe management was worried that if they notify everyone early, nobody will report to work anymore, or could cause sabotage and damage their work.

well we are all professionals and no one wants to burn bridges. but if that is what they think, do they mean that the 6 people wont do that? i think they only thought of deciding on announcing to notify everyone when lots of wuestion arise why there were only 6 when all of us had the dec 15 proj end. if retrenchment is the reason why people will loss their jobs, then it should be the sole reason and it must have been applied equally to all.