This is true.
I’ve had this communicated to me by more than one of the niche coffee houses here in Chattanooga; longer roasting = less caffeine.
Here’s a semi related tip, caffeine doubles the impact of certain pain meds. I have to take a few different meds during the day for chronic pain, and I can halve the dose by taking it with coffee.
Less drug, more coffee, no downside!
There’s a number of prescription and OTC pain meds that have caffeine to boost their effects.