The Lockpicking Lawyer is not a thief, so I don’t get your desire to incorrectly nitpick. Especially when you clearly understood the point.
"A is demonstrating a proof of B" does not require "A is a clause in B".
A being TLPL, B being that the entire lock industry is bad, so bad that anyone with experience would be a massive improvement, for example a thief.
Other people have commented to further explain the point in other words. I recommend you read those, perhaps it’ll make you understand.