Proposition
Seller or listing counts describe a stock of supply, not the probability of a successful match. That probability also depends on availability, quality, distribution, demand intent, ranking rules, and transaction completion.
Evidence state
Foundational two-sided-market models establish the importance of interactions and cross-side effects. They do not, by themselves, prove how a specific operational supply metric affects liquidity on a particular platform.
Counterargument
In a supply-constrained micro-market, additional supply may be the binding growth lever. The proposition rejects only the use of aggregate supply volume as a sufficient diagnosis.
Test
Estimate marginal changes in fill rate, time to match, unmatched supply, and completed transactions after supply growth, separately by micro-market and controlling for demand changes.