Detrimental? I take it you mean to the Axis winning the war?
The thing that makes the Magnetron and associated technology's handover so significant (to me) is not necesarily the material contribution that it made. The other massive significance is in the sharing of extreme cutting edge technology between two states (even before one state had entered the war), not something that happens very often, and an indication of the surprising levels of trust that were being achieved (despite other differences) between two world powers. There's also the significant concession being made by Great Britain in admitting that the Americans were the only ones that could take the technology onwards, not an easy thing to accept in a state that was only just getting inklings of the retraction from Empire and decline of it's previously huge power on the world stage. Suez was 16 years away but there were, perhaps due to the war, immediate signals of potential future decline.
Cheers,
Adam.