New to the forum and thankful for all of your great info! Thanks.

I’m slowly acquiring tools to begin my journey timber framing and have purchased a Hudson Tool Co. framing chisel off eBay and need to do a little work on it to get it in operation. In Jack Sobons book, “Hand Hewn”, he says:
“The back of the chisel blade should not be flat. I know this seems counterintuitive, but if it is slightly arching (convex) along it’s length, the user can control how much chisel is cutting by rocking it slightly on the curved back…. 1/16th over the length of the blade…..”

Can I hear some opinions on this for a beginner? Is this just a preference or is this quite common. Seems like most other literature says to make them flat.

Thanks