Thanks for the informative answer Bone. So if someone puts on a 100 lot Jul/Aug spread (in CL for instance), I'd presume that's additional hidden liquidity the outright would have to get through in order to move past it?
The exchange will either match firm outright liquidity, or elements from other spread orders ( crosses ), or block trades, or even confirmed RFQ's.
Yes, for the more liquid futures the implied pricing DOM looks substantially different than the naked outright DOM. Especially for highly liquid inter month products like Crude Oil and Nat Gas, Grains, STIRS... etc...
The spread bid / ask liquidity is almost always MUCH more substantial than the flat price outrights. Been that way since forever.
To your point, if there was a 300 lot Aug outright order at a parallel price level working and also a 500 lot Jul/Aug spread order working that matched both the Jul and Aug pricing -
the exchange would internally Iceberg another 200 lots in Jul at that price level as long as the Aug order remained firm in order to fill the entirety of the Jul/Aug exchange supported spread order.
Yes, the exchange injects liquidity internally in terms of matching bits and pieces of other orders to fill implied spread orders. BIG TIME. And since spread orders are typically much larger than the flat price orders, it can absorb a great deal of liquidity.