Would you ever run into a situation where that would make any difference?
The FARs say you must land at the nearest suitable airport in point of "time". That's not necessarily your takeoff alternate. You may very well have to get rid of fuel rather than trying to save it.
Even if it was close to one hour away, with single engine climb to altitude and all the other stuff you'd be doing, I doubt you'd be at altitude long enough for it to make any difference.
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