You don’t need chapter and verse on fare construction, just like for like booking and all charges including fees must be included in the comparison fare. BA will ask for completion screenshots as far as final pricing.

also note for others that many other start countries now work and you need to upload screen shots with the claim. There’s a new claim form and process. I had a £60 out of the £389 Y sale returns to LA a couple of weeks back. They’ve also taken to jiggery pokery with rounding so it’s not always double the difference, they round to nearest multiple of £5 low or high and then double.