I’ve had more than a few classes on circuits throughout my schooling, from high school physics to my mechanical engineering college coursework. Please enlighten me as to where my logic is flawed.

Two sources wired in parallel can supply more current than either individual source can supply on its own. The wiring on each parallel branch will have identical voltage, and the converged branch will carry the sum of the currents. Total load of 20 amps exceeds the capacity of the wiring, breaker doesn’t see the full load and doesn’t trip.