That's the theory, anyway. I've never seen any measurements to support that belief; only "it stands to reason" and the like. Similar claims are often made regarding curved versus straight forks, and yet straight forks are as common as curved forks on performance bikes these days.

In the sixty years that I've been riding track and road bikes constructed of different materials and with different geometries, I've never been able to detect any difference in shock transmission that I can't attribute to wheelbase differences. In fact, it appears that head tube angles are chosen solely to achieve a desired wheelbase, with comfort being a consequence of the wheelbase choice, not the head tube angle. Lower average speed, more upright rider position: slacker head tube angle, longer wheelbase. And the reverse for higher average speed.