You can believe whatever you want, but I can guarantee that if you go to any triathlon club, and some folks have finished the equivalent distance of a 140.3 race, even if it was not WTC-branded, you'd be considered a spoilsport and a total doof if you went in there and said "well, you're not REALLY an Ironman because it wasn't a WTC event."
The vast majority of triathletes will accept that if you finish a 140.3 distance race, even non-WTC, by the cutoff, you can call yourself an ironman.
(By your criteria, I haven't finished a half-ironman as I've never done a WTC event, even though I've done 4 of 'em.)