I wouldn't be so sure he fished the Grand River but I would expect that the latest FLW Outdoors tournament director is not completely up on some of our more odd regulations. If Randy didn't say where he fished, then the tournament director wouldn't be able to make a ruling on it even if he was aware of the weirdness of drop-shotting being illegal.
Maybe Randy used a 3" leader? Some of the FLW staff are aware of the drop-shot rule too so there are a number of possibilities. I consider it not important enough to get very excited about it. Anymore than I got excited when Larry Nixon admitted his winning bass he caught on St. Clair in the Bassmaster years ago was foul-hooked.
It shouldn't have counted by I'm glad I'm not the tournament director who, after announcing he won, found that out and then had to pull him aside and say 'you didn't win' because you didn't catch that bass legally. They were looser on local regs even back then. They try to be tougher but they still don't always know all the local regs - though they should, especially the uncommon rules limited to the rarely-fished Northern states.