Should I worry about inconsistency / “cracks” in cedar posts?

Not at all.

“Checking” happens when cedar dries, the exterior surface (sapwood) shrinks quicker than the inner surface (heartwood).
The result is the familiar “check” which is neither a split nor a crack.

All of posts have heartwood in the center, which helps aid in the strength and longevity of our materials.

Checking will not pass through the heartwood, so there is no fear of the material splitting in half or subverting the structural integrity.