Maybe this whale was tracking tail numbers, drove down to the executive airport, and saw that Cisco's chief M&A guy had a huge grin on his face as he stepped onto the plane.
(Okay, I doubt that highly, but it is a scenario)
The real trouble with 'maybe they were legit outsiders' is the options expired specifically today, which means you need to know _when the announcement_ is to profit.
For example, a Printer for Business Week and a Stock Broker traded on pre-publication information and were convicted of insider trading.
https://corporateinsiderstrading.wordpress.com/2012/02/01/bu...
For those who don't know, they're both part of the same metro area (Bay Area) but they're 50 miles apart, anywhere from 1 to 2 hours apart depending on traffic.
They traded on information that was non-public at the time of the trade. Why shouldn't that be treated exactly as trading on news of this merger before it was announced? (The merger was eventually going to be known to the public as well, right?)