It's still possible that the guys from Monacor didn't lie and were quite creative.Impedance ratio is the square of the voltage ratio. 2:1 voltage ratio translates into 4:1 impedance ratio.
It is a versatile transformer with different connection combinations.
To obtain only galvanic separation, or sound coloring, in a 1:1, 600:600 configuration, windings 1-2-3 and 6-7-8 must be identical, as electrical, electromagnetic, mechanical, etc. parameters.
Then we could connect as in the sketch and get the impedance ratio
1200:300 i.e. 4:1, so voltage ratio 2:1