OP asked about TTI suggested about preventive use of WD-40, and that is all but ignored in the replies here so far.
No offense meant but
I'm guessing it's being ignored as it sounds like pass the buck BS, to me anyway. Having owned a classic car resto/ repair shop for 25 years the only coating that has held up over time is Jet Hot or VHT.
That was my take, too. I only asked on the odd chance that there was some merit to it. I had never hear of spraying anything on headers. At least as a protectant. Believe me, we have tried many. The manufacturer applied coatings are a flat rip off IMO. One is lucky if they hold up more than 1-2 years in the collector area and near the exh ports
That has been my experience, too.