I guess what would bother me is that it looks like a store bought cake and a typical lunch run to subway - not a party with any real amount of forethought. One of those "Oh it's so and so's birthday? Oh crap, I guess I'll run to the strip mall during lunch break and get something." Awkward moments like that, when people feel obligated to acknowledge an event to assuage their own guilt about forgetting it, are why I don't tell coworkers when my birthday is!
I guess for those who don't know about his religious conversion it seems a bit jarring that this example of 80s excess is having such a low key birthday affair. But otherwise not really notable given the context.