3/5 of other persons

That is the bigotry in the Constitution.

It implies all people not named, and that left indentured servants of arbitrary contract length.

That was the deal in 1787, most folks knew it was appearing, but not yet of consequence. At that time it was an emerging contradiction in an otherwise lousy labor law system. It was left at 3/5 because they were still people, these 'other persons'.

Barely bigotry, the real stuff, legal racist mass agricultural labor,  really started around 1810. At the time it started, in agricultural American, it seemed no worse than Mexican farm labor in California.  It gets economically significant from then on.

Mechanical machines were starting to solve the problem by 1850. We could have skipped the Civil War, bought out most of the lousy labor contracts and gotten labor rights established sooner. Lincoln's point, really.