If it IS the same programme I think they do mention it, and the reason:
due to UK's huge debts to USA for their help in WW1 and WW2, and due to Lend Lease and other arrangements, UK was obliged to "share" all its new technology with US. Having supplied jet engines to US, UK decided it was unreasonable to deprive the other great power of this technology and causing an imbalance of power, especially as the Russians also were/had been allies. The same basic British jet engine was on both sides of the battle, and for a while the Russian MIG was clearly using this engine in a more manoeuverable air-frame with devastating effect.