The heartwood is naturally stiffer due to less moisture as
@runeshrenik correctly described. Just like
@smilley792 pointed it will perform early due to the stiffness. It also cracks as the moisture holds the fibre together. Pro's need bats to play in early and are less likely to be concerned with cracking as they get them replaced and have spares in the kit. They can afford to treat them like a rent-a-car as top tier players never purchased them and therefore don't need to worry about maintaining them.
For a amateur you need to carefully oil and accept that the heartwood will probably not last as long as sapwood. I had a 3/4 Aussie BOSS Menace and used it one game it went well from first ball and edges flew off the stiffer heartwood and nearly cleared the boundary. My main scoring shot that day 😬
Sapwood will take take longer to reach its peak and perform the same if not better once played in.
I personally hate knocking heartwood on other people's bats as it is brittle. I oil it a bit more and have to take it easy when knocking it. Sapwood is supple once oiled correctly and does not crack as easy.
@d7bow's B3 would have required almost no prep due to the B3 stiffer press. I note it is well oiled.