Fly them through Poland or through Romania - it doesn't matter. It was never about logistics. The reason Poland wanted to do it this was to involve US and Germany indirectly in the deal.
That means Ukrainian MiG-29s crossing into Ukraine from Poland.
If Poland had simply handed over the planes to the Ukrainians in Poland, the result would have been... Ukrainian MiG-29s crossing into Ukraine from Poland.
If Poland had instead handed over the planes to US troops in Poland, without moving them, and the US had then handed them over to the Ukrainians, the result would have been... Ukrainian MiG-29s crossing into Ukraine from Poland.
So you get exactly the same result in all three cases. What Poland doesn't want is Ukrainian MiG-29s crossing into Ukraine from Poland.
> or through Romania
Yes, that's what this is really about.