This video shows working seal twisting mechanic like it was on retail tbc server.
Retail proof:
• Seal Twisting
Note from a forum:
After my movie that I released a bit ago it has become a hot topic. Many people have been watching that video front to back over and over to try to figure out how to do it. It is actually 10x simpler then what some of you are making it out to be.
You swap seals when your swing animation, of any sorts, happens. Even if it isn't a seal of command proc you can swap seals and still have SoJ proc off your white attack with this method. Seal of Command MUST be your starting seal, from there you can swap seals to any of the other seals that are procs. However, the only ones that would serve a high benefit is Seal of Justice, and for those lucky souls, Seal of Blood.
Seal of Command has a 1 sec internal cool down, also the reason it wont proc off of windfury or reckoning twice. These mechanics where put in place because before you could swing with a white attack and then your seal of command could be out of range, so they put them closer together, and this was their method.
Exploiting or creative use of mechanics? No one knows except Blizzard, but this is a make-shift substitute for a spell interrupt that is long over due.
TL;DR:
1. put on seal of command
2. right as your swing animation happens (normal, socomm proc, or crit) swap seals to SoJ or SoB
3. Profit
Practice on mobs first, it helps if you are binding SoJ to a simple key bind. Also know that because of GCDs it will be very hard to juggle your seals with your Crusader Strike up, so prioritize carefully.