The key, I think, is to distinguish between topics that remind you of other topics, and topics that, upon being comprehended, actually help you understand other topics.

D&D rules remind you of D&D content, which helps you understand fantasy literature. D&D rules, by themselves, though, don't help you understand much of anything else.

Likewise, baseball helps me understand antitrust law enforcement, because baseball has a Congressional exemption to antitrust laws. The exemption has virtually nothing to do with the infield fly rule, though. The infield fly rule reminds me of baseball, but by itself it sheds no light on antitrust law enforcement.