I think the comment was supposed to point out that Monier is supposed to be one of the principle inventors of reinforced concrete and that he passed away in 1906 ... hence trying to figure out how the gentleman in the story fit in.

Maybe he invented the currently used formula for reinforced concrete?

What formula? It is concrete reinforced with rebar. My guess is the OP just misremembered the specific thing the patron invented. It's a great story either way.

Might just be misremembering the specific retort he made - he is famous for use of reinforced concrete. (I checked that after the last time I told the story, to make sure I hadn't invented that part.)