Steepness doesn't have to refer to a graph of time versus skill, and at any rate the metaphor certainly predates machine learning curves. As others have pointe

Steepness doesn't have to refer to a graph of time versus skill, and at any rate the metaphor certainly predates machine learning curves. As others have pointed out, it's meant to evoke the difficulty of climbing a steep hill versus one that's flatter. This person is mixing concepts and etymologies amidst an insufferable air of superiority.