I'd also add stem length, stem angle, spacers, saddle, bibs or padded liners, handlebar shape and width, shape of the brifters, handlebar tape, shoes etc. 😃
You can't narrow down "bump absorption" to a single brand. It depends on so many things and it's not something you can measure, you just go by feel. Also big tyres absorb so much anyways.
For example the OP added Cannondale to the "comfortable bike" list. An older CAAD9 was the harshest riding road bike i've ever tried.