Originally Posted by seawolf
Maybe it's market specific.
T fare NYC-NRT waive for upgrade to higher fare.
S fare (recent European sale) NYC-MUC waive for upgrade to higher fare.
Could be that too.
Like other fare rules, they follow patterns, not absolutes. It's good policy to read the fare rules before you purchase a ticket. I once was about to buy an ORD-PHL for $192 RT and after asking what the rules of the fare were, the agent volunteered a WA fare for $109 each way. The WA fare was 100% refundable and thus the better value for me.