There is a science called "complex system theory".
The basic outline: If you respond to complex problems (like an exponentially spreading virus outbreak) with a simple solution, it is inevitable to fail.
There are many, many examples in history.
EDIT: And Boris is as simple as simple can be.
Is it a complex problem though? Or is it pretty simple - a virus is spreading which needs to be contained. Time will tell whether "flattening the curve" was the correct approach.
Agreed - Boris is an ass-hat. However, for once he's actually deferring these decisions to medical professionals.