I don't see any reason to be worried. Since you dont have any performance mods and the extended warranty is in place, everything should be covered. Hopefully the recent service records should suffice IF they ask for them. If they insist on older records, go back to the place that you got it serviced at and ask them to print a copy.
Also, please post in the thread below as well for the benefit of the community, where people report failures on 15+ WRX
https://forums.nasioc.com/forums/sho....php?t=2749732