I just cant see the Borg allowing holidays and birthdays.
Its an isolationist technique. Isolating.
And,,, it takes focus away from the Borg to the individuals. Think of all the focus the Borg will lose if individual JWs could celebrate birthdays. This is what John on his ExJw-analyzer video pointed out one time.
And isolation. This has worked for years and years for the Borg,,,,why would they change it now.