I'm not sure where the WWE gets 16 reigns for Ric Flair. I count several more than that. Let's go through them.
His first reign was from 9-17-1981 to ?-?-1982
2nd from ?-?-1982 to 1-6-83
3rd from 1-10-83 to 6-10-83. The NWA doesn't recognise the first 2 losses, and consideres these all one reign.
4th from 11-24-83 to 3-21-84
5th from 3-23-84 to 5-6-84
6th from 5-24-84 to 7-26-86
7th from 8-9-86 to 9-25-87
8th from 11-26-87 to 2-20-89
9th from 5-7-89 to 7-7-90
10th from 1-11-91 to 3-21-91
11th from 5-19-91 to 9-8-91
Ric Flair also became the first WCW World Heavyweight Champion on 1-11-91, holding it until 7-1-91 for his 12th world title. He held this concurrently with 2 of his NWA title reigns, so some may consider them all 1 reign.
Ric Flair won the WWF World Heavyweight Championship on 1-19-92 andh eld it until 4-5-92 for his 13th world title.
14th 9-1-92 to 10-12-92(WWF)
15th 7-18-93 to 9-?-93(NWA)
Ric Flair became the first WCW International World Heavyweight Champion upon WCW's departure from the NWA in September 1993, holding it until 9-19-93, for his 16th world title.
17th 12-27-93 to 4-21-94(WCW)
18th 4-21-94 to 7-17-94
19th 12-27-95 to 1-22-96
20th 2-11-96 to 4-22-96
21st 3-14-99 to 4-11-99
22nd 5-15-2000 to 5-22-2000
23rd 5-29-2000
So, if you don't count the 2 NWA Disavowed reigns, you're down to 21. If you don't count the 2 WCW International reigns, you get 19. Discount the 2 NWA Reigns concurrent with the first WCW Reign, and you're down to 17. I have no idea which other reign they drop.