Why it matters
The useful buyer check is whether the board, locking edge and product sheet match the selected range or product code.
The role of calcium carbonate
Calcium carbonate helps create a firm core. It supports weight, density and dimensional feel, but it does not provide stickiness by itself.
It helps the plank feel firm.
It supports structure and heat resistance.
It needs PVC to bind it into a usable core.
The balance problem
A low-cost formula may increase calcium carbonate to reduce material cost. When that happens, the same binder has to hold more powder.
More powder can make the plank heavier.
More powder can also increase brittleness risk.
The lock edge is where this risk often appears first.