This is a point where you're not quite wrong, but you're not quite right either.
The Big Gold Belt did not represent the NWA World Heavyweight Championship. It represented the WCW World Heavyweight Championship. The WCW at that point was allied with the NWA and was the "home promotion" of Ric Flair, who was both the NWA and WCW World Heavyweight Champion for the majority of the time (an exception occurred in March of 1991, when Tatsumi Fujinami defeated Flair for the NWA World Heavyweight Championship but Flair remained WCW World Heavyweight Champion; during that time, Flair continued to carry the BGB as the WCW World Heavyweight Champ). When Flair left WCW in July of 1991 and went to the WWF, he took the BGB with him (coincidentally, WCW would declare their WHC vacant in July and crown Lex Luger as the next WCW WHC while NWA would wait until September to vacate their title and subsequently crown Masahiro Chrono as the new NWA WHC). The belt that Flair took with him was owned by Jim Crockett Promotions/World Championship Wrestling, not the NWA, and Flair refused to return it due to his deposit not being paid back by Jim Herd (who ran WCW for Turner). WCW commissioned a new BGB. When Flair, after a settlement was reached between WWF and WCW with Flair as a third party (or between Flair and WCW with WWF as a broker...it wasn't an open legal proceeding, but a business deal so the records aren't publicly accessible), returned the BGB, it was used as the title belt for a subsidiary of WCW called "WCW International" and represented the "WCW International World Heavyweight Champion", the position it filled until the WCW International WHC was unified with the WCW WHC.
The BGB would continue to represent the WCW Champion (along with the other designations it was given along the way) until the unification of the WCW and WWF Championships into the Undisputed WWF Championship by Chris Jericho in 2001 and the BGB would be temporarily retired in 2002.
The BGB would be brought back in September of 2002 as the "Undisputed WWF Championship" had become disputed due to the unwillingness of Undisputed Champion Brock Lesnar (who was "exclusively signed" to Smackdown) refused to recognize any contenders from Raw, thus causing Raw GM Eric Bischoff to declare the title "disputed" and leading to him awarding the World Heavyweight Championship (represented by the BGB) to Triple H. The BGB continues to represent the World Heavyweight Champion and Randy Orton carries it to represent that half of the "WWE World Heavyweight Championship".
Meanwhile, the NWA World Heavyweight Championship has been represented by a different title belt altogether (the classic belt displayed above) whenever the WCW and NWA WHC's were different people, and then exclusively since the split between WCW and NWA.
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