Twitter may ban cryptocurrency advertisement on their system but thus this mean that you cannot make a post about cryptocurrency. Also did twitter really made a statement about this or this could be another FUD. Many are making a move to topple down bitcoin and also many are making false news. Thus we must be careful and do some research before believing this kind of stuff.
There is a possibility that these news are fake, so people who know this kind of information can buy bitcoin and altcoins much cheaper before the blow. Anyway the market gets affected and many traders use it for manipulations on the currency.