Subaru: Customer responsible for diagnostic fees for cars under warranty

I posted a while back about our experience with Open Road Subaru here in Vancouver, BC. Parking brake light on 2013 Subaru Outback comes on intermittently while driving. The dealership ran diagnostics and found a calibration failure and determined that a sensor in the parking brake needed to be replaced at a cost of $1600. After posting about the cost of the repair on this forum, someone directed me to a TSB from 2019 that extended the parking brake assembly warranty on all GEN 4 Outbacks by 15 years. I contacted the dealer about the TSB and they looked it up and agreed that the repair was covered. But they still charged me almost $200 for the diagnostic. I argued that I should not be charged for diagnostics for a warranty covered issue. The service department representative said they did not know it was a warranty repair when they performed the diagnosis and therefore I was responsible for paying the diagnostic fee.
I sent a detailed complaint to both Subaru Canada and Subaru America on July 6th, including a detailed description of what happened and copies of the work order and payment. Subaru Canada has yet to respond. Today, Subaru America sent me this response:

Hope all is well, thanks for getting in touch, sorry for your experience. Glad to hear the repair was covered under warranty. Regarding the diagnosis fee, which is the responsibility of the customer, we would not be able to provide a refund. I apologize for the inconvenience. Have a nice day.
sincerely,
STYLE
Subaru of America, Inc.
Department of Consumer Advocacy

So, in this rather short answer, Subaru is saying that diagnosing warranty repairs is “the responsibility of the customer”. My Subaru Outback was bought used so this is the first time dealing with a Subaru warranty. I can tell you that having owned a new Ford Escape Hybrid and new Toyota 4Runner under warranty in the last 25 years, I have never been burdened with diagnostics for warranty covered repairs, so this is something unique to Subaru. One thing I know for sure, I will never buy a new Subaru with warranty.