Yup, Rustoleum BBQ black is very flat. I recently painted some things with BBQ black and others with Rustoleum semi-gloss black "Painters Touch 2X" (Ace Hardware was having a twofer sale at the time) and the BBQ looks ashy LOL
When I bought the BBQ black at Home Depot they also had Rustoleum high-temp engine paint in flat black, it was like $2 more and had a lower temperature rating than the BBQ....not thanks