That thread wasn't meant to say that ALL stock thermos are that far off. My point is that the stock themos are USUALLY off according to numerous posts and threads on this forum. So just going by IDEAL without checking it with something accurate first can really have you way off. Kudos to you for checking yours and knowing what temp IDEAL actually is.
I did not do that before I seasoned mine. Imagine the difficulty I had trying to get mine to the HOT range as the instructions called for.
I warped the heck out of the stock charcoal grate.
I did find out however that the SnP IDEAL is adjustable so you can set the IDEAL pointer to be whatever your favorite smoking temp is. But since you can buy a replacement from Brinkmann for about $3, I wouldn't put a whole lot of faith in their accuracy over time.