I'm a carnivore who eats 2 lbs of beef a day.
As someone who started consuming wagyu ground beef (sourced here) on daily basis, I can confirm that there is a huge difference in the taste compared to conventional ground beef.
Marbling is not the only factor. Remember that much of the meat flavour is in the fat.
The Beef Heel of Round represents a cut from the beef round immediately above the hock. This roast is composed of many small muscle groups, has a lot of seam fat, and is one of the least tender cuts of beef.
Braising for long periods of time works best for that cut.
Bottom round is rump roast and the top part furthest away from the hock.