It’s OK to run a discount for Steam Keys on different stores at different times as long as you plan to give a comparable offer to Steam customers within a reasonable amount of time.

Where in valves policy is it showing they’re affected. That right there is from the link you provided, literally stating its fine to have discounts on different stores. Steam provides the keys for free and still eats the cost of hosting the game if one of these keys are sold on a different store.