> Why would not the same apply advice to oil and gas contracts?
Because oil & gas suppliers only ever sell one product, and memory fabs can dynamically switch product mix in response to supply & demand to optimize profits. The same sand, power and water can make DDR4, HBM or DDR5
Oil and gas suppliers have several products: gas, diesel, jet a, propane, naptha, asphalt etc.
Aren't the proportions is those essentially static?
Depends a lot on the oil field, geology is random