And "the fall of the pound after Brexit" is not the same as "the fall of the pound caused by Brexit". 

A delighful clarification!

True, they are not the same. But they are not independent either.   We have had a good series of major announcements now and they are all surrounded by reports of 'pound rises/falls in expection of/following a Brexit announcement."

It should be no surprise to anyone that votes and announcements have effects. Analysing what proportions due to what is more difficult.