Mac I occasionally will use a weed burner to do a couple things with my grates. But not all the time because extreme high heat and/or thermal shock can (not "will" but "can") cause warpage if its over done.
If I want to recondition a rusty grate, in a rush, I'll use the weed burner to heat it, slow & even, to help loosen any scaly rust. Then it can be brushed clean enough to begin a new seasoning process. The weed burner works great for loosening build-up from sugary sauces like teriyaki or KC style sauces.
A quick sanitization is another good use for the weed burner, it'll heat up a strange grill in a few minutes and with proper oil/heat combo added during the process you'll end up with a nearly perfectly seasoned grill grate in minutes. Might not be non-stick but your burger wont taste like iron, that and expecting a working grill grate to be perfectly non stick 100% is crazy.
IMO the trick is too heat the grate slow & even, without getting it red hot, or holding the weed burner in one spot to long.