Perhaps this was just an oversight on an employee's part. Perhaps this was just filling both containers with milk as half/half was not available at the time or at that location.
The way to know for sure was to ASK.
While this may have been an annoyance (at best) and I get it, but it could have been rectified in real time. I remember preparing a bowl of delicious fruit and beside the offerings was a large container of what I thought was whipped cream - turned out it was sour cream. I plopped on a huge portion over my fruit, sat down, took a bite of peaches and "cream" - GAH! I simply returned to one of the attendants, let them know what was happening and they corrected the error.
Calling it a lie, IMO, is an overreach.