@Cassandra I would call it "the seller tries to spam their product into as many categories as possible" and the customer is none the wiser.
Would be nice if an e-commerce "crowd-sourced" products category improvements and that de-prioritized spammy products.
On the other hand, the usual product ontologies may also simply not be up to fine-grained-enough categorization.
@J12t
Some of both, I'd say. Platforms try to cover the most common filters, but they'll never think of everything--and it would be cumbersome if they did.