My understanding CJ is that the flights that were missed involved crew struggling to get back to AMS or BRU and that we are now looking at maybe rostering standby days down route to keep guys at out stations rather than allow them a quick visit home.
There is no restriction that I know of on leaving SIN on an OFF day and I have to say that management have been very accommodating with my roster; allowing me to leave SIN 12 days before my AALV starts.
I stand to be corrected if you know different.