Like you I don't believe it.
Mostly because we have still managed to stay slightly above the EU trend growth.
I have seen a constant stream of forecasts since before the referendum, all relating to Brexit, and the forecasts have been wrong, all too pessimistic.
I do not doubt that some investment decisions have been held back. These decisions will still have to be made and as I worked for a relatively large German owned international company for a number of years I'm pretty sure they would just sit on their hands until they have clarity, unless there is a real pressing need for them to make an urgent decision.