I'm not sure the chocolatier's site with no numbers or data is a good reference. This study shows the ratio of theobromine to caffeine is like between 2.5:1 and 25:1, with most between 5:1 and 10:1 [1]. To your point it's not zero, but it's by far the minority bitter alkaloid constituent.

[1] https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2621....