Having been involved with 6 different 777 operators on 200ER, 300 & 300ER their Limitations restricted Autolands to F20/30, however this is not to say that F25 Autoland certification trails have not been carried out, maybe a Boeing engineer can give input, I assume that any certification for an Autoland flap setting will involve many landings at different weight/wind/CG limits, F20/30 would normally give an operator sufficient options...