I think one thing that needs to be clarified here is what the 31st relates to. 

On December 16, the Chinese government, through a deputy director of the PBOC, unofficially met and  ordered 10 third-party payment providers of virtual currencies among them the biggest, Alipay, to stop providing clearing services to the Bitcoin exchanges with a time limit of 31st January 2014.

http://finance.yahoo.com/news/bitcoin-price-halves-china-clampdown-085816934.html

However, instead of waiting until the 31st of January, 3rd party payment processors terminated services effective immediately.  As of right now, depositing and withdrawing funds from Chinese exchanges is not done through 3rd party payment providers. This is why, as the OP states, the 31st is pretty much irrelevant at this point

However, Huobi and OK Coin are using their corporate bank accounts to process deposits/withdrawals.  Some (including myself) argue that this is against the PBOC's new regulations on Bitcoin, which state that:

"financial institutions and payment institutions are not allowed to use bitcoin...or directly or indirectly provide customers with other services related to bitcoin"

and also states banks

"may not act as a central counterparty in Bitcoin trading"

In my opinion, Huobi (and OK Coin) are operating outside of the PBOC's bitcoin regulations (and I argue are not adhering to many more regulations) and are at risk of being shut down at anytime. However, this has nothing to do with January 31st.