Out1 has the signal on the center pin, and the earth on the outer one. Same thing for Out2.
However, the Boost have a signal on the center pin, and another signal in the outer one.
So if you put the "A" probe of your oscillo in the center pin of the boost, and "B" probe on the outer pin, you get one of the two signals travelling through the boost. If you revert the probes, and put probe "A" on the outer pin, and probe "B" on the center pin, your oscillo shows you the other signal. Both signals don't mix until they enter your body.
Spooky, isn't it?
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