Missydarlin has clarified before that upfaring to nonrefundable P fares doesn't waive the change fee. I noticed that same language before, and I assume it means as it says-- an actual F fare class refundable First.

The website will charge the change fee if it applies (MVP or non-status, after 24 hours of purchase, etc.). Phone agent may or may not waive the change fee, depending on the agent. I had one that was going to charge the change fee, but offered to upfare to K without a change fee, allowing the use of a GGU. Which didn't make sense to me.