@Tom ******
. Ive done it at Changwatanna 6 times . First 4 it was required. Last two times they said " not necessary".
I kept it there anyway, because they have a habit of doing whatever they feel like at times. Every extension I did seemed to be different between the officer you get when applying. Ask 3 people there and you'll normally get 3 different answers to your questions.
The last two times i applied they said keep it there, only to be told on collection it wasn't necessary. Welcome to CW IMM