I'm done doubting his ability to beat the 5000 WR. I find the claims that he could go sub 12:30 unrealistic, though.
But does he actually stand a chance at the 10000 WR? No current athlete has got closer than 20".
He weights aprox. 15 kg more than Chep and 20 more than Kiplimo/Aregawi/Barega.
Considering he would have to run the last 5000 alone, isn't his morphology (1'87/75 kg) too "big" for wind resistance, heat dissipation...
...and carrying these 74/75 kg every stride?
For instance, Joshua is pretty tall for a distance runner (1.83) but below 60 kg, so he benefits from stride length without the "big" (again, for a distance runner) frame.
Kejelcha is barely his same height weighting at least 15 kg less.
TL;DR: Jakob's frame could be too big for 10000 & up distances.