If my understanding (just being based on the number of counts in each measure in the given staff) is right then two added time signatures only mean that in one measure, there will be 6 beats and a quarter note still gets one beat. Is this correct?
It's down to the rhythm within each bar.
A more obvious time signature would be 6/4. But 6/4 is compound time, and is generally understood to have two stong beats per bar, as: ONE two three FOUR five six.
But that isn't what the composer wanted here. They wanted: ONE two three four FIVE six. writing the time signature 4/4+2/4 makes this more clear.