Nobody is saying they have to invent a system, just fly a non-precision approach the way their books say to. Everything offered on here has been how some of us do it to ensure least risk of a vertical profile cock-up. They WILL have been trained in the use of VNAV final approach descent (or if not they were breaking the rules). Problem is they didn't do it properly. There are sure to be many factors, but in my opinion they didn't minimise the risks before starting the approach and then didn't execute the briefed approach that well.
I agree with the above statement, however if they had been trained in the use of vnav final approach descent then they cocked up because it cannot be used for an approach not encoded in the fms data base.As such they are prohibited from using vnav and should have been vs or fpa.