What did you understand Kas to mean by his use of the term "lean misfire"?

He wrote, about that term, "...but I think most people understand what the
term means."

Maybe he defines that somewhere -- but someone who writes about a
technical matter and throws out a term and states "I think most people
knows what that means" are writing at a technically unacceptable
level.

If a chemistry book uses the term "stoichiometric", gives no
definition but states most people know what that means, there'd be a
lot of unhappy chemistry students, especially when it came time to
fail their test.