I think it’s more like not explaining it in terms of the economic conditions for which slavery really provided the basis for. Like the northern merchant economy vs the south planter class. When anyone could essentially get free real estate, convincing people to work the land to generate profit required coercion. Indentured servants since colonization were used, “white” slaves even preferred, but the existing trade networks like the Dutch were really instrumental in providing the means to extract profit from the land. Racism and white supremacy didn’t cause this, they developed out of this arrangement, the purpose of which was to produce cotton, corn, etc.

Slavery was crucial though because the public campaign against chattel slavery in the north was very real and a major contributor to the public acceptance and motivation for the war. The US as it exists today was essentially built between the Civil War and WW1, and reducing it to just slavery is really not explaining everything, but also it really was “about” slavery in many ways. So I just say yes it was about slavery, but also everything around slavery, and the things that made slavery “necessary” for that economic system to function.