Unless Nitrogen is not going to issue you the segwit2x coins, there is really no point in withdrawing.
They are not going to issue the segwit2x coins, thus the post.
Just to inform you, even exchanges disable withdrawal and deposit of bitcoins 24hrs (or even 48hrs) before a fork happens. It's a normal procedure for them to be able to access how much of the altcoin they are going to give out to each user. I do think it is fairly reasonable to do so as it prevents the possibility of over sending the newly created coin.
Which exchanges have disabled withdrawals??? I've heard of such in the past but I think we're over that at this point. BTW, this is a snapshot that is scheduled to occur, not yet a hard fork.
I was able to withdraw from Nitro no problem FWIW. Back when the bitcoin gold snapshot was happening, I tried to withdraw my coins 16 hours before but unfortunately they held my coins for 24 hours. They didn't say it was because a fork was coming, they said it was because it was a large withdrawal and that new procedures meant that large withdrawals would routinely take 24-48 hours going forward.