Panera sells their coffee is a 16 and 20 fl oz sizes, not 8-16. For the dark roast coffee in a 20, it has 268 mg of caffeine.
They sell the charged lemonades in 20 and 30 do oz sizes. The 20 size generally has 260 mg of caffeine, slightly less than an identical volume of coffee, with the exception of the drive-through servings which is even lower due to ice.
What reasonable person would not consider a nearly identical caffeine per volume to be a fair interpretation of “contains as much caffeine as our dark roast coffee” when both can be ordered in the same 20 ounce size?