Is it a valid comparison to say that learning to sell and learning to swim share a common characteristic in that both skills are best acquired through hands-on experience rather than relying solely on theoretical knowledge from books?

All skills rely on a combination of domain knowledge (knowing what and why) and procedural knowledge (doing). You have to learn both.

When you learn domain knowledge, you organize it for a purpose — which could be passing a test or using it when you perform a skill. If the domain knowledge is taught for the wrong purpose, you can prevent the learner from ever using it for performing the skill. Thus teaching it in the wrong way causes damage.

There is also an important different between selling and swimming. The former is mostly verbal learning. The latter is a mix of verbal, perceptual and psychomotor learning. Since the way you teach is controlled by the type of knowledge you are teaching, you would teach selling and swimming in very different ways.