I just come across the following PDF page in Internet:
http://www.espoma.com/pdf/garden/GI_4.pdf

It says that we should deep water the lawn. But it also says this:
"During the summer, much of the root system deteriorates.
Therefore, summer waterings should be light and frequent."

This is new to me. I am under the impression that we should always
water the lawn deep, not "light and frequent".

Can someone help me to understand that suggestion?

Thanks.

Jay Chan