Once a deliverable contract enters its delivery month it stops behaving like a trading vehicle and starts behaving like a claim on the actual commodity. Exchanges impose much smaller spot-month position-limits, and convergence with the cash market becomes the dominant force.
Speculators are expected to be gone. Brokers enforce this with liquidation-only settings before first-notice-day, and any position left is at the mercy of whoever still wants the physical barrels or bushels.
Example: CME caps spot-month live cattle at 450 contracts against 6,300 in all other months combined. The tighter cap exists because a large spot position can distort delivery.
Related: position-limits, convergence, first-notice-day, physical-delivery, delivery-notice