'these 2 gals have been virtually untaxed by previous 11.5 laps & can bring nearly all their open 400 speed to the last lap'
No, if that were the case they could keep up their 10km pace for 30km+ The energy system for sprinting has been little used though and it is this plus the knowledge the finish is close which gives them the extra surge on the last lap, as well as the fact they were not all out for the full distance
You will never admit to being slightly wrong however so just do your best!
They would not crush the rest of the world over 1500m either although they might do well. If they could they would or at least would need to change their training. Likewise if KB trained for middle distance he would be a lot closer to the best, although its still horses for courses and his is longer distance
The op has got the last lap times wrong and any one who thinks youtube can give them an accurate lap reading is mistaken