For the last two months, they have said they plan to add it. In fact, Bitcoin Cash was about 280 dollars and it was common knowledge Coinbase was going to support it. You, the employees, and everyone else could have loaded up if you wanted to.
Lastly, there is no real incentive for employees to load up on BCH to make a quick buck. In the first seconds of trading a massive sell wall of 12,000 orders emerged and that would drive the price down dramatically.