I'm not scientist, I think I've provided ample evidence of that numerous times.  I read the Hedge Knight report and that claim, that the heart is not a pump, it definitely jumped out....not for a scientific reason, but more because it is something that challenges what has long been considered a fact.  This is something I appreciate...I like it when long established "facts" are challenged....

I'll give an example of a long accepted "fact", one that entire schools of medical training accepted for more than 2,000 years...right up until the 1800s, even into the early 1900s there were those who could not let go of a "fact" that had been totally disproven.  The notion that disease was casused by the humours in the blood being out of balance....the bleeding of patients was something that was accepted wisdom going back to Roman times, it was orthodoxy, something that one challenged at their peril....skeptics were pillored as quacks...."give me a break, everyone knows that its the humours in the blood being out of balance that causes disease".

Here's an interesting article on the matter of whether or not the heart is a a pump:

https://www.rsarchive.org/RelArtic/Marinelli/

Here's a part of what that site says:

The fact that the heart by itself is incapable of sustaining the circulation of the blood was known to physicians of antiquity. They looked for auxiliary forces of blood movement in various types of  `etherisation' and `pneumatisation' or ensoulement of the blood on its passage through the heart and  lungs. With the dawn of modern science and over the past three hundred years,  such concepts became untenable. The mechanistic concept of the heart as a hydraulic pump  prevailed and became firmly established around the middle of the nineteenth century.

The heart, an organ weighing about three hundred grams, is supposed to `pump' some eight thousand liters of blood per day at rest and much more during activity,  without fatigue.  In terms of mechanical work this represents the lifting of approximately 100 pounds one mile high!  In terms of capillary flow,  the heart  is performing an even more prodigious task of `forcing' the blood with a viscosity five times greater than that of water through millions of capillaries with diameters often smaller than the red blood cells themselves!