Let us assume that Jonathan is deceiving us and that this is a marketing ploy... what does it matter? We haven't been conned into spending our time or money on anything. The card still works in the same way.
Now, if Jonathan is telling the truth then it sucks for him to be treated in this way. It seems to me that there is nothing to lose by believing him.
Sure, it sucks to be misled and I'm sure it hurts some people's pride to think that they are prone to being tricked but ultimately we don't lose anything!
For me it comes down to a nice example of how generous some people can be. And if Starbucks are actually the ones topping up the card then yay, free coffee!