Interesting. This sounds like the kind of shedding I've seen only with Scotch 226. It does make me wonder how corrupt the used tape trade has become at this point. I've seen a lot of tape that has been put on different reels accidentally or on purpose. God knows how much of this went on during the "Tape Scare" in 2005 when Quantegy first filed for bankruptcy.
Sellers like "TapeandTape" and other eBay sellers wanted to sell whatever would fetch the highest price. 996 and GP9 were going for stupid money, so if a guy had empty reels and boxes for those tapes I'm sure the temptation was great to put whatever pancakes they could find on those reels. Could be old discarded 226 or 456... or possibly bad runs of 996 that should have been destroyed by 3M when returned for replacement, but found its way back on the market.
Well anyway, just remember... if it's not sealed its not new, and may not be the tape that the reel and box says it is.