That's a good point. They studied the stats for the book Numbers Game and:
"Corners are next to worthless; given the risk of being caught on the counterattack, with your central defenders marooned in the opposition’s box, their value in terms of net goal difference is close to zero."
And with our lower than average conversion rate I'd bet our net goal difference over the last 5 years is minus something.
Probably best knocking it short to retain rather than hitting front post every time.