I think he was just joking around, dont take it too seriously.
The Weber Kettle lid is 23in in diameter.
The bowl of the Kettle is 22.5in in diameter.
Ill post some pics later tonight for you to see. I suggested you get a Weber Kettle not to cook on but to use for measurements and designing. It might be a good idea to check that all these middle sections fit perfectly on a Kettle before it leaves your factory to avoid any problems.