The issue raised by the OP illustrates what appears to be one of CO's current pricing strategies. That is, CO seems to use Y fares to make the benefits of elite status more in-line with the revenue generated by the customer on a per-flight basis. So, the elite who spends more on a given flight will be rewarded, like the Gold who spends $100 more for a Y fare over the Platinum on an H fare.

When a flight does not generate much revenue by the time of departure (i.e., when there are F seats left after all A fares and Y-ups are accounted for), CO will then reward its elites based on status and then fare paid. So, the elite benefits are still distributed somewhat on a "value" basis - the Gold on a B fare will get trumped by the Platinum on an X fare, but, presumably, the Platinum generates more revenue overall for CO.