This absolutely happens. Usually, however, the regulators are interpreting the law in a way that the legislators agree with. In those cases, there is no need for new legislation.
One, not every securities professional trades at a bank. Two, this is not true for any of them. Broadly speaking, work-related written communications must be logged. But there is nuance and exception to that.
The offense here is that no effort was done to keep records of the communication. It would have been ok to use WhatsApp if they somehow would have archived all communications. Records of communications have to be kept so that auditors can verify that no inside trading secrets were communicated to others, for instance.
any change to any banking system is then done via a banking order (payment order, deposit order, etc) and is documented and signed.
so there is plenty of trail evidence for each transaction with each customer
